AMON User's Guide. Author: Andrej Simon Creation date: 11-Mar-2009 Last changed: 11-Aug-2010 AMON Version: 0.32

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1 Author: Andrej Simon Creation date: 11-Mar-2009 Last changed: 11-Aug-2010 AMON Version: 0.32

2 Contents 1 The monitoring tool AMON Some examples of using AMON...1 Starting AMON...1 Wait events monitoring with AMON Introduction to AMON Preparing to run AMON...1 Downloading and running the AMON executable...1 Checking the terminal font...1 Getting started with AMON...3 General Usage AMON By Examples Database sessions overview...1 The top sessions ( s and ss ) windows...1 Static session details (the z key)...5 Dynamic session details (the Z key)...10 I/O performance statistics...11 Datafile statistics...11 I/O statistics from the V$SYSSTAT view...13 Monitoring the wait events statistics...14 Monitoring the database processes with high PGA consumption...14 Work areas of SQL cursors...15 ASM I/O performance statistics Available performance screens AMON screens for database instances...18 B - Buffer cache details...19 D - Database files I/O statistics (only in Oracle11g)...21 d / dd - Datafiles and tempfiles information...21 E - System events from V$SYSTEM_EVENT...21 EE - Wait classes from V$SYSTEM_WAIT_CLASS...21 e / ee - Wait events from V$SESSION_WAIT...21 G / GG - Segment statistics...22 g - General information...22 h - Help window...22 I - Instance I/O statistics...22 II - Database functions I/O statistics (only in Oracle11g)...23 L - Currently running long operations...23 l - Locking details...23 ll - Latch statistics...24 M / MM - Mutex statistics...28 m - Instance memory...28 n - Network statistics...29 P - Process memory (PGA) details...29 p - Parallel execution details...29 r - RAC statistics...29 S - SGA information...29 s / ss - Top sessions views...29 Z - Dynamic session view...30 z - Static session view...30 i

3 t and tt - System and session time model statistics...31 w - Active SQL work areas...32 AMON screens for ASM isntances...33 D - ASM disks I/O statistics for each ASM client. (Only in Oracle11g.)...33 d - ASM disks statistics...34 g - General information about this ASM instance...35 L - Active ASM long-running operations...36 m - ASM instance memory overview AMON command-line options a AMON default output directory b {y n} c count d database alias e {b t a} l {y n} p database password P Oracle process ID number r {sysdba sysoper sysasm} s seconds S Oracle SID number u database user v w AMON start window Overview of dynamic performance views used in AMON Database instances...1 B - Buffer cache details...1 z - Database object details (see z for segment statistics G )...1 D - Database files I/O statistics (only in Oracle11g)...1 z - Database file details for D...1 "d" - Datafiles Information...1 "dd" - Tempfiles Information...1 "z" - Datafile/Tempfile details for d and dd...1 "E" - Waiting events from V$SYSTEM_EVENT...2 "z" - System event details...2 "EE" - Wait classes from V$SYSTEM_WAIT_CLASS...2 "e" - Grouped waiting events from V$SESSION_WAIT...2 "ee" - Waiting events from V$SESSION_WAIT...2 z - Waiting events details (see the static session details in s )...2 Z - Waiting events details (see the dynamic session details in s )...2 G/GG - Segment statistics...2 z - Segment details...3 "g" - General instance information...3 z - System parameters...3 "I" - Instance I/O statistics...3 II - Database functions I/O statistics...3 z - Database function details...4 "l" - Locking details...4 "z" - Locking details...4 'll - Latch statistics...4 z - Latch details from ll window...4 ii

4 Z - Child latch details from ll / z /2...4 L - Currently running long operations...4 z - Session details (see the static session details in s )...4 Z - Dynamic session details (see the dynamic session details in s )...4 M - Mutex sleeps statistics...5 MM - Mutex sleeps history statistics...5 z - Mutex details for M and 'M...5 "m" - Instance memory overview...5 n - Network statistics...5 "P" - Process memory (PGA) overview...5 z - Process details (see the static session details in s )...5 Z - Dynamic process details (see the dynamic session details in s )...5 "p" - Parallel execution information...5 z - Session details (see the static session details in s )...6 Z - Dynamic session details (see the dynamic session details in s )...6 "r" - RAC statistics...6 "S" - SGA overview...6 "s" - Top sessions overview...6 "ss" - Top sessions overview with waiting events...6 "z" - Session details (static snapshot without refresh)...6 Z Dynamic session details with automatic refresh...7 "t" - System time model overview...7 "tt" - Session time model overview...7 "z" - Session details (see the static session details in s )...7 Z - Dynamic session details (see the dynamic session details in s )...7 "w" - Active SQL work areas overview...7 "z" - Detail work area view...7 ASM instances...8 D - ASM disks I/O statistics for each ASM client. (Only in Oracle11g.)...8 z - ASM client details...8 d - ASM disks statistics...8 z - ASM disk details...8 g - General information about this ASM instance...8 L - Active ASM long-running operations...8 m - ASM instance memory overview AMON Keys Overview Database instance...1 B - Buffer cache details...1 z - Buffer object details...1 D - Database files I/O statistics (only in Oracle11g)...1 z - Database file I/O statistics details...2 "d" - Datafiles Information...2 "dd" - Tempfile Information...2 "z" - Datafile/Tempfile details ("d" or "dd")...3 "E" - Waiting events from V$SYSTEM_EVENT...3 z" - System event details ("E")...3 "EE" - Wait classes from V$SESSION_WAIT_CLASS...3 "e" - Grouped waiting events from V$SESSION_WAIT...3 "ee" - Waiting events from V$SESSION_WAIT...4 G - Segment statistics (part 1)...4 iii

5 GG - Segment statistics (part 2)...4 "g" - General instance information...5 z - Displaying system parameters...5 "h" - AMON keys overview...5 "I" - Instance I/O statistics...5 II - Database functions I/O statistics...5 L - Currently running long operations...6 "l" - Locking details...6 z" - Lock details ("l")...6 ll - Latch statistics...7 z - Latch details...7 Z - Child latch details...7 M - Mutex statistics...7 MM - Mutex statistics...8 z - Mutex details...8 "m" - Instance memory overview...8 "P" - Process memory (PGA) overview...8 "p" - Parallel execution information...9 "r" - RAC statistics...9 "S" - SGA overview...9 "s" - Top sessions overview...9 "ss" - Top sessions overview (waiting events view)...10 "z" Static session details...10 "Z" Dynamic session details...11 "t" - System time model overview...11 "tt" - Session time model overview...12 "w" - Active SQL work areas...12 "z" - Work area details ("w")...12 ASM instance...13 D - ASM disks I/O statistics for each ASM client. (Only in Oracle11g.)...13 z - ASM client details...13 d - ASM disks statistics...13 z - ASM disk details...14 g - General information about this ASM instance...14 h - Help window...14 L - Active ASM long running operations...14 m - ASM instance memory overview...14 iv

6 1 The monitoring tool AMON AMON is a free interactive tool for performance monitoring of Oracle databases and ASM instances. A lot of performance monitoring and tuning information is available in the dynamic performance views and some fixed views. AMON displays this information very fast on any UNIX terminal. All used views are documented in this manual (see Overview of dynamic performance views used in AMON), so that you can read more about a specific view in the Oracle database documentation. The tool is written completely in C programming language. It uses Oracle Call Interface (OCI) API and UNIX Curses library. This allows AMON to run on every UNIX terminal. After downloading the tool, you can immediately use it. (If SQL*Plus can run, then AMON should execute as well.) AMON executes only SELECT statements, so that you can easily test it on your database. No database changes are made by AMON. The AMON tool is developed by Andrej Simon, Oracle ACS Germany in my free time. If you have any questions or comments, please contact me directly (andrej.simon@oracle.com). The AMON tool is available from the following Internet URL: Some examples of using AMON Starting AMON At first you should set the required Oracle environment variables, as you would usually do before starting SQL*Plus. The preferred method of using AMON is to execute it directly on the database server. You should set the ORACLE_SID environment variable and start the tool as the user with SYSDBA privilege. (See Downloading and running the AMON executable for all required steps.) The AMON will start and the general information window will show up. 1-1 The monitoring tool AMON

7 The first row shows the hostname, the instance name, the connected database user and the current refresh interval. The available keys for this window will by displayed in the second row. By pressing the h key you will get the overview of all available AMON windows. (This help window can be displayed from any other window.) 1-2 The monitoring tool AMON

8 Wait events monitoring with AMON To get an overview of the running Oracle instance you usually would like to see the wait events statistics from the view V$SYSTEM_EVENT. Please, press the E key to get the calculated delta values for the last refresh interval. 1-3 The monitoring tool AMON

9 Often the DBA would like to see, which wait events the current database sessions are waiting for. You should use the ee window (by pressing twice the e key) to get this information from the view V$SESSION_WAIT. 1-4 The monitoring tool AMON

10 Even if only 3 user database sessions are active on this database, more sessions are shown because of the background processes etc. Every database instance will have got many inactive sessions. To hide all idle sessions on this window you should press now the i key. This would hide all sessions waiting for the wait events from the idle wait event class. This way only really interesting sessions are visible and you could immediately see the blocked session. 1-5 The monitoring tool AMON

11 The session with SID 136 is waiting for the TX lock. Usually a DBA would like to get more information about such a session. You should select the session of interest using the keys f, b, j and k. You can scroll one screen forward( f ) and backward ( b). Please use the j key to move the line up and k to move down. The currently selected row is highlighted. You can now press the key z or Z to get the static or dynamic session details. The dynamic session view reselects the session details accordingly to the refresh interval. The data in the static session view will be fetched only once before showing them. See Static session details (the z key) for further details. 1-6 The monitoring tool AMON

12 The static session view ( z ) presents a lot of session details. You can see, for instance, that this session is blocked by the session with SID 140. Staying on the session details window, you can press some number keys to get other available information about this session. For instance, by pressing the 2 key you will see the currently running SQL statement from the view V$SQL for this session. 1-7 The monitoring tool AMON

13 The 3 key will display the working execution plan from the view V$SQL_PLAN. The key 5 will show the information from the view V$ACTIVE_SESSION_HISTORY. 1-8 The monitoring tool AMON

14 Often you would like to save all this information for later analysis. In AMON you should press the 0 (zero) key to save all session details in a text file. This could be especially helpful, if the session state or the running SQL statement could change and you want to collect the diagnostic information about this session state. 1-9 The monitoring tool AMON

15 The session was saved into the text file with a unique file name in the current directory The monitoring tool AMON

16 2 Introduction to AMON AMON is an interactive performance tool for Oracle databases and ASM instances. The tool helps to monitor the running instance by displaying important performance statistics. It's especially useful for monitoring the performance statistics in near real time (like the UNIX top utility). The AMON tool is available from the following Internet URL After copying the AMON executable to the target machine, you can immediately start to use it. The tool executes only simple SELECT statements. No PL/SQL code, views etc are installed on the target database! All AMON SQL statements have got a comment /* amon */, so that you can easily identify them in the SQL library cache or in a AWR/Statspack report. Preparing to run AMON Downloading and running the AMON executable 1. After downloading the AMON executable file, you have to copy it to the desired database server. AMON uses UNIX Curses API for writing on the screen, so that you don't need any X-Windows features. (PUTTY is just enough!) Usually you would rename the downloaded file to amon like this: mv amon_hp amon 2. In the next step you should give AMON the execution rights, for instance: 3. chmod 755 amon 4. Make sure, that the Oracle environment is set up correctly. You can try to run SQL*Plus, because AMON uses the same OCI shared libraries. 5. If your operating system user belongs to the DBA UNIX group, then you can just type in amon. AMON will connect to the running instance as the database user SYS. (The environment variable ORACLE_SID should be set up correctly.) This is the preferred connection method for using AMON. 6. You can also use the options -u (User) -p (Password) and -d (Database) to connect to any database with a specified user. Make sure, that this user has the DBA privilege for selecting from dynamic performance views. You don't need to specify the password on the command line. If you have specified a user with a -u option, AMON will ask you for the password on its own. Checking the terminal font AMON works best with the fixed terminal fonts, which enables to draw the lines with Curses library. If you see the following characters on you PUTTY screen instead of the lines, then your PUTTY font don't support this. (The default PUTTY font don't work in some cases.) 2-1 Introduction to AMON

17 In this case you can either start AMON without the drawing the lines (amon -b n) or you should change your font for the current window in your PUTTY configuration. Go to Change Settings>Window>Appearance and click on the Change button near in the Font settings area. Now you should choose another font. On my PUTTY the font Courier New works just fine. So choose your desired font and confirm it with Ok button. Now you have to confirm it with Apply button once more. Try now to start AMON again. This is an example after changing the font to Courier New. 2-2 Introduction to AMON

18 AMON may work with the default font as well. But some screens could look bad and some functions like scrolling by row wouldn't work properly. The same problem with fonts could also occur on Linux with KDE or GNOME terminals. In this case you should try to use another font or to run AMON using the xterm. The default font for xterm works fine for me in the most cases. Getting started with AMON General Usage AMON shows different database performance statistics in the different screens. The list of available screens (help window) can be called by pressing the "h" key. You can call this help window from any other window in AMON. After connecting to the database AMON checks at first the value of the parameter INSTANCE_TYPE. Depending on the value (ASM or RDBMS) different performance windows are available. The function keys and the keypad keys can send different codes on different UNIX terminals and 2-3 Introduction to AMON

19 different UNIX operating systems. That s why AMON completely avoids the function and keypad keys. You should work with the tool using one-key commands only. For instance, the key h presents the help information screen and the key q stops AMON. You don't need to press the Return button after pressing any of these keys! The user selects a desired performance window by using a letter key. Every screen has got some special keys, which function are only available in this screen. These keys are shown in the second row of the AMON screen. This row with available keys is refreshed every 3 seconds. So you could just wait for a while to see all available keys. All available keys are also documented in this manual. (See AMON Keys Overview.) Usually, the available keys are the number keys, which are used to change the ordering column for the output. The currently used ordering column has a highlighted column heading. Often the available keys also include the "#" key (ordering by SID, File-ID), the & key (ordering by database user in some view), the i key (filtering out the idle events, sessions or locks) and the z key for showing the details (zooming in). For instance, just pressing the "d" key in AMON shows immediately a datafiles performance statistics. Usually, the performance counters are cumulative. AMON calculates the delta values for the required refresh time (see the first row in AMON screen) and shows these calculated metrics. Pressing one of the number keys 1, 2, 3, 4, 5 would order the output by physical reads pre second (the highlighted column), average read time, average blocks per read, single blocks read and physical writes per second on the datafiles performance screen. This allows you to quickly find out the interesting performance values,for instance, the datafiles with high number of I/Os. You can look for the available order keys in the second line of AMON window. This line is refreshed every 3 seconds independent of the refresh interval. But you could also just try to press the number keys to change the sort order. (Apparently not all columns can be used as ordering 2-4 Introduction to AMON

20 ones.) The highlighted column will show you the currently order column. You can't break AMON by pressing the key without any function in the corresponding window! So you should just try it out. You can scroll the pages in AMON by using the keys "f" for forward and "b" for backward. On the page you can scroll to the next and the previous rows using the "j" and "k" keys (like in vi). Every refresh moves the highlighted row to the top position. If you look for a specific row, such refresh could disturb you. In this case it could be useful to increase the refresh interval by pressing the + key, so that the new refresh doesn't reorder the rows. (You can anytime decrease the refresh interval again by pressing the - key.) Why to scroll to a specific row? Because often you would like to get additional information about the highlighted row. In such cases you can press the "z" key (zooming in) or Z to get the further details for the current row. You can leave such details view window by pressing the "z" key again. 2-5 Introduction to AMON

21 3 AMON By Examples After starting AMON, the new user should press the "h" key to get the AMON help screen. You see the current instance name (instance identifier for a RAC instance), connected database user (SYS) and the refresh interval (10 seconds) in the first row. You can change the refresh time by pressing "-" or "+" to cut by half or double the refresh time. Database sessions overview Often a DBA checks the available database sessions to find the top consumers for a specific resources. The top sessions windows s and ss are based on the information from the views V$SESSION and V$SESSTAT and help to locate such consumers. The top sessions ( s and ss ) windows This is the picture of the s window. 3-1 AMON By Examples

22 The window header shows the number of sessions and the consumption of some resources during the last refresh interval. The database session details like SID, serial number, database process ID (SPID), database user name, session status (A for active) and program are shown. The sessions are ordered by the logical reads statistics (the default order). You can see that, because the logical reads column is highlighted. As usual in AMON the number keys will sort the information or toggle some columns. (You should check the available keys on the second row!). For instance, if you are looking for the sessions with a lot of redo log activity, you should press the key 4 to re-order the sessions by redo size. 3-2 AMON By Examples

23 In this way you can quickly find out the top consumers by CPU, logical reads, physical reads, redo size and physical write. You can also sort the sessions by SID or by SPID, if you are looking for the special session. Sometimes you would like to see the similar information from the the views V$SESSION and V$SESSTAT together with wait events details. The is the task for the ss window. (You should press twice the s key to get there.) 3-3 AMON By Examples

24 The default sort order on this window is the waited time in seconds. But you can also order by resource consumption statistics like the s window. Often many database sessions are connected but only some of them are of interest. To hide the idle sessions the key i should be pressed on such sessions windows. 3-4 AMON By Examples

25 The pressing of i key on the ss session will hide all sessions, which current wait event belongs to the idle wait event class. The i key on the s window hides the sessions with the status not equal to ACTIVE. On the picture above you can see, that only 6 sessions are remained. Often these are exactly the sessions, which you would like to analyze further. Let's see, how we could get more details about these sessions. Static session details (the z key) After locating a session of interest you often would like to get more details about it. By pressing the z key in s or ss windows you would get the static session details about the highlighted session. The static means, that all session details for the specific session are selected only once before entering the z window. No session details will be re-selected independent from the refresh interval. This allows you to analyze the specific session details, even if the session state has been changed in the meantime. The session details window shows the session details from different dynamic views. You can switch between them by pressing one of the number keys, which are shown in the second row on the screen. You can always leave the static session details window by pressing the z key again. The first (default) session details window shows mostly the information from the view V$SESSION. (You can go back to this screen by pressing the 1 key.) 3-5 AMON By Examples

26 If the session is blocked and the database will recognize it, then the blocking session information will be available in the view V$SESSION. AMON shows such information on this screen as well. For instance, on this screen you can see, that the current session with SID 140 is waiting for the TX lock and is blocked by the session with SID 136. By pressing the 2 key you can get the current SQL statement for this session. 3-6 AMON By Examples

27 The execution plan for the SQL statement is displayed after pressing the 3 key. 3-7 AMON By Examples

28 You can try out all available keys, which are displayed on the second row. For instance, the 5 key will show the details from the view V$ACTIVE_SESSION_HISTORY. 3-8 AMON By Examples

29 Often you need to save all this information for the further analysis. This is very simple in AMON. You should just press the 0 (zero) key and all displayed session details will be written to the text file with a unique file name. 3-9 AMON By Examples

30 The find name will be displayed. Dynamic session details (the Z key) Sometimes you don't want to select the session details once, but to fetch the current details for a specific session on every refresh interval. This is a purpose of the dynamic session details window. The information is similar to the static session details (the z key), but it's re-selected on every refresh interval. This way you can monitor, how long the session executes the specific SQL statement or stays in the specific wait event. You can see the dynamic session details using one of the following methods: Pressing the Z key from one of the session view windows (for instance, s or ss ). By pressing the Z key from the static session details window. Sometimes you want to monitor a specific session with AMON. If you already have got the SID or database process ID from other tools, then you can start AMON with -S or -P option into the dynamic session details window AMON By Examples

31 I/O performance statistics AMON User's Guide Let's assume, that we need to check the I/O statistics. In this case you could use the following windows in AMON: d, dd or D for the datafiles and tempfiles performance statistics I and II for performance statistics on the whole database I/O operations B for the largest database objects in the database buffer cache G for segment statistics from the view V$SEGMENT_STATISTICS Datafile statistics You should press the "d" key to get the I/O performance statistics for datafiles from the view V$DATAFILE. At first the delta values from the cumulative statistics for the first refresh interval should be collected. So we need to wait a refresh time. (Default refresh time is 10 seconds.) After that you would see, for instance, the following performance information. The datafiles are ordered by the physical reads per second. That's why the column heading for 3-11 AMON By Examples

32 physical reads is highlighted. The special keys for this screen are shown in the second row. So you would see, that you can press the "f" or "b" keys to scroll page forward or backward. You can move to the next or previous row using the "j" and "k" keys (like in vi). Usually the number keys are used to order the statistics. The order by physical reads is forced by pressing the "1" key (default sort order on this screen). You can press now, for instance, the "2" key to order the datafiles by average read time. The highlighted column heading will be changed to average read time. This way you can easily sort the datafiles to find out, for instance, the datafiles with the most physical reads or with the slowest average read time. Let's say, that we would like to see more information about the data file 1. So we press the "z" key to get more details (zooming in) about the highlighted row AMON By Examples

33 Pressing the "z" key again would bring you back to the datafiles performance view (the previous window). The available keys in the datafile details window. By pressing the 1 or 2 keys we can see the file details (the current window) or the file histograms. I/O statistics from the V$SYSSTAT view Let's say, we would like to see the I/O statistics for the database instance from the view V$SYSSTAT. We need to press the I key for that. If you don't know the corresponding key, then you could check the help window (the h key) for that. The I window provides you the following delta values for the cumulative statistics during the last refresh interval AMON By Examples

34 In the window header you will see the number of read/write operations and the read/written bytes per second 1, 5, and 15 minutes ago. These numbers could help to compare the current load to the load in the last 15 minutes. You should try out the other I/O performance windows to see the available statistics. Monitoring the wait events statistics Usually the wait events statistics should be checked, if performance problems are occurred. The following AMON windows presents different wait events metrics: E, EE, e, ee and ss. Usually you would check at first the E and ee windows. See the examples of working with them in Wait events monitoring with AMON. Monitoring the database processes with high PGA consumption Assume, that some database processes are consuming too much memory. In this case you would use the "P" key to get the information about the allocated PGA for each of database process AMON By Examples

35 The default sort order is by allocated PGA memory. Work areas of SQL cursors Let's say, that a DBA needs to check, which sessions are using work areas at the moment and which of them are writing down the temporary data into the temporary tablespace. In this case the work areas window (the "w" key) can help AMON By Examples

36 If a work area doesn't fit in the memory and the session writes this work area into the temporary segment on the disk, then the column "Disk size" would have a non zero value. On the window we can zoom into the selected work area with the z key and check the SQL statement. This statement requests the selected work area. In the z window you can press the 3 key to see the execution plan for the SQL statement. The highlighted execution step in the plan has requested the work area. You can, of course, save the information about the selected work area into the file with the "0" (zero) key. ASM I/O performance statistics With AMON you can also monitor the I/O performance statistics of the ASM instance. After creating a database session, AMON checks at first the value of the parameter INSTANCE_TYPE. For ASM instances AMON presents the following window AMON By Examples

37 As usual you can see the available AMON screens by pressing the h key. To see the ASM disks statistics from the dynamic view V$ASM_DISK_STAT you should press the d key. Per default the disks on this window are sorted by physical reads during the refresh interval. Using the number keys (see the second line) you can of course change the order. By pressing the z key the details for the highlighted ASM disk will be shown on the next window AMON By Examples

38 4 Available performance screens You can see the available screens in AMON by using the "h" key. Some screens are only available for the database release Oracle11g. These screens are not shown in the help screen for the Oracle10g databases. AMON supports both database and ASM instances. Depending on the value of the instance parameter INSTANCE_TYPE the different performance screens exist for ASM and the database instance. AMON screens for database instances. Key B D d dd E EE e ee G/GG Screen description Buffer cache details Database files I/O statistics (only in Oracle11g) Datafiles information Tempfiles information System events from the view V$SYSTEM_EVENT Wait event classes from the view V$SYSTEM_WAIT_CLASS Grouped events from the view V$SESSION_WAIT Waiting events from the view V$SESSION_WAIT Segment statistics 4-18 Available performance screens

39 g General information h AMON help page I Instance I/O statistics II Database functions I/O statistics (only in Oracle11g) L Currently running long operations l Locking details ll Latch statistics M/MM Mutex statistics m Instance memory overview n Network statistics P Process memory (PGA) details p Parallel execution details r RAC statistics S SGA information s Top sessions information ss Top sessions information by waiting events t System time model statistics tt Sessions time model statistics w Active SQL work areas + Double the refresh time - Cut by half the refresh time B - Buffer cache details This window shows the 50 largest database segments from the database cache. The objects from all buffer pools (default, keep and recycle) are shown. Using this window you can check, which database objects consume the large part of the database cache. If you have configured the KEEP buffer pool, then you should see the corresponding objects on the top of all objects. Using the z key you can get additional information about the corresponding database object Available performance screens

40 The SELECT statements from the V$BH view in AMON are rather expensive. You may consider to increase the AMON refresh interval (the + key) in this window for the database instance with a large cache. AMON will try to use the underlying fixed view X$BH, if the connected user has got the required SELECT privilege. If the database cache is large, but you can't connect to the database as the user with SYSDBA privilege, then the SELECT statement could execute rather slow. In such a case you should consider to grant the connected database user the privilege to select from the fixed view X$BH. Unfortunately it's not possible to execute the GRANT statement on a fixed view directly. SQL> grant select on x$bh to andrej; grant select on x$bh to andrej * ERROR at line 1: ORA-02030: can only select from fixed tables/views The solution is to create a view as SYS user and to give the user the privilege to select from this view. a) Run the following statements as the SYS user. CREATE VIEW X_$BH AS SELECT * FROM X$BH; GRANT SELECT ON X_$BH TO ANDREJ; b) Connect as the AMON user (in this example as ANDREJ) and create a synonym on the created view V_$BH Available performance screens

41 CREATE SYNONYM X$BH for SYS.X_$BH; AMON User's Guide Now AMON will use the X$BH for the SELECT statements on this window after connecting as the database user ANDREJ. D - Database files I/O statistics (only in Oracle11g) The view V$IOSTAT_FILE in Oracle11g complements the previously available views V$FILESTAT and V$TEMPSTAT (see the d and dd windows). The D window shows the I/O statistics from the view V$IOSTAT_FILE. By providing the latency time for I/O operations and by separating the small and large I/O operations, this window is a useful extension to the d and dd windows. The z key on this window will provide further details for the corresponding database file. d / dd - Datafiles and tempfiles information These are classic performance windows to look for I/O statistics over the datafiles and tempfiles. The performance statistics are selected from the views V$FILESTAT and V$TEMPSTAT. In the window header AMON shows the number of physical reads and writes 1, 5 and 15 minutes ago. Use this numbers to compare the current I/O load to the previous one. By pressing the number keys ( 1, 2 etc) you can order the datafiles by different statistics like physical reads, physical writes. This way the files with critical response time can be easily identified. By pressing the z key the additional information for the corresponding file will be shown. E - System events from V$SYSTEM_EVENT The view V$SYSTEM_EVENT contains the cumulative statistics for the wait events. This AMON window displays the delta values for wait events together with used CPU time during the last refresh interval. EE - Wait classes from V$SYSTEM_WAIT_CLASS Since Oracle10g all wait events are grouped into classes. This windows shows the time totals (delta values) for all registered classes from the view V$SYSTEM_WAIT_CLASS during the last refresh interval. e / ee - Wait events from V$SESSION_WAIT Usually the wait events statistics indicate, that Oracle process had to wait for an event to complete, before the execution could be continued. That's why the wait events often reveal the performance problems in some specific area or for a specific session. The view V$SESSION_WAIT contains wait events for all active sessions. To display only active waiting events AMON uses the predicate WAIT_TIME=0 in these windows. The e window groups the events by the event name and 4-21 Available performance screens

42 allows you to see at a glance, how many sessions are waiting for the same event. The ee window shows all database session, which are currently waiting for some wait event. Since Oracle10 the idle wait class is introduced. In both windows you can press the i key to hide the sessions, waiting for an event from the idle class. This allows you to analyze only really working sessions. Using the z or Z keys you can get the further session details. Both windows re-select the data at every refresh interval and don't maintain the delta values for the wait events. If you like to see, how often the events are occurred or how long sessions were waiting for the wait events during the last refresh interval, then you should use the E window. G / GG - Segment statistics These windows show segment-level statistics from the view V$SEGMENT_STATISTICS. Using the number keys 1, 2 etc. you change the displaying statistics(logical reads, segment scans, physical reads etc). The windows present max. 100 database objects with the highest statistic numbers. g - General information This is the default window, which shows some important database information (some parameters, size of online redo logs, database character set etc). The information on this windows usually doesn't change during the refresh interval. h - Help window This window shows all available performance windows with the corresponding keys. In the upper left corner you can see the current AMON version. I - Instance I/O statistics This window helps to check the current I/O operations. The header shows the number of read / write operations (per second) and the amount of read / written bytes (per second) 1, 5 and 15 minutes ago. The I/O statistics are selected from the view V$SYSSTAT. AMON presents the the delta values during the last refresh interval. The window displays both the whole I/O load and the usage of database cache ( cache and direct I/Os). This screen indicates the I/O requirements of the database and helps to estimate the impact of possible database cache enlargement. You could get more I/O relevant details from the II window (Oracle11g only). For the information about the I/O datafiles statistics you should use the windows d, dd and D (Oracle11g only) Available performance screens

43 II - Database functions I/O statistics (only in Oracle11g) The II window provides additional information to the I window. The header shows the number of read/write operations (per second) and the amount of read/written bytes (per second) 1, 5 and 15 minutes ago. The dynamic view V$IOSTAT_FUNCTION (Oracle11g only) displays the database statistics for database functions (like database buffer cache or archiving operations). The window II is based on this view and shows the delta values for the last refresh interval. This information allows you to see, which database component are responsible for the most I/O operations. For the additional I/O details you should check the I window, which is based on the statistics from the view V$SYSSTAT. The further I/O datafile statistics are located in the d, dd and D (Oracle11g only) windows. L - Currently running long operations This window shows the statistics for the long-running database operations from the view V$SESSION_LONGOPS. This view displays the status of various operations that run for longer than 6 seconds (in absolute time). You could use this window to check, if some long-running operations are currently running. For instance, usually this window should be empty during the business hours for a OLTP database. The additional information for the displayed long-running operation can be fetched with the z key. l - Locking details This window is based on the view V$LOCK and helps to find out the sessions, which are currently waiting for a database lock. (Such sessions can also be located by looking for the sessions with the corresponding wait events in ee or ss windows.) The data on the l window is ordered by the lock requested mode column. If a database session requests a lock and has to wait, then such session will have the requested lock mode value greater then 0. If the requested lock is granted, then the requested mode value will be set to 0 and the column lock mode will show the granted lock. The columns ID1 and ID2 shows the additional information about the locks, which allows to group the lock requests for the same resource together.(see the description of the view V$LOCK for more information.) 4-23 Available performance screens

44 Usually the database always maintains some locks, so that this window will never be empty. But the ordering the sessions by requested lock mode shows the currently waiting session at a glance. (This is the session with SID 143 on the picture above). If you see a session for a longer time with a requested mode greater then 0, then you should investigate it. The z key will provide you additional details about the blocked and blocking sessions. ll - Latch statistics This window shows the aggregate latch statistics from the view V$LATH. The latches can be requested both in willing-to-wait mode and in no-wait mode (immediate). The default window shows the delta values for willing-to-wait latches only Available performance screens

45 The latches are ordered by misses ratio (misses/gets). You can order the latches by the name ( 1 ) and by the waited time ( 4 ) as well. Pressing the key 5 toggles the displaying of the statistics for latches in no-wait mode. You can order the latches by immediate misses ratio (immediate misses/immediate gets) using the 3 key. If some latch shows too high misses ratio, you would like to get more details for this latch by pressing the z key Available performance screens

46 The latch details window shows the statistics from the view V$LATH view together with the information from the view V$LATCH_MISSES. Some latches consists of many latches (latch children) and the information in the V$LATCH is grouped for all of them. To see the latch children statistics for a special latch from the V$LATCH_CHILDREN view, you should press the key 2 on the corresponding latch details window Available performance screens

47 Sometimes special latch children shows more contention than others. You can get the details for a specific latch child by pressing the Z key. The cache buffers chain latch contention is often occurred because of the repeated access to one or more hot blocks. For this special latch AMON provides the information from the fixed view X$BH Available performance screens

48 The values of the touch buffer count help you to find the hot blocks. (See the My Oracle Support document How To Identify a Hot Block Within The Database Buffer Cache with the Doc ID ) You must have the SYSDBA privilege to access the fixed view X$BH. (See B - Buffer cache details for the steps to grant a usual database user the privilege to access the fixed view X$BH.) If your buffer cache is large, then many cache buffers chain latch children are available. The SELECT statement in AMON on this window may be slow. You should consider to increase the refresh interval in this case on this window. M / MM - Mutex statistics Starting with Oracle 10g some latches were replaced by mutexes. These windows present the information from the views V$MUTEX_SLEEP and V$MUTEX_SLEEP_HISTORY. Usually these windows are empty, because there are almost no long mutex sleeps. m - Instance memory The Oracle instance memory allocation consists mostly of SGA and PGA. This window shows the currently allocated memory for both of them and the allocated caches inside of the SGA. The instance memory management can make use of the automatic memory management with the MEMORY_TARGET parameter in Oracle11g, automatic shared memory management with SGA_TARGET or the old static memory management. AMON shows the the currently active memory management model on this window as well Available performance screens

49 This window often helps to provide the quick answer for the memory requirement of the running instance. n - Network statistics This window displays SQL*Net client statistics and SQL*Net database link statistics from the view V$SYSSTAT. In Oracle11g some new RMAN statistics for DUPLICATE operations etc. are available from the view V$IOSTAT_NETWORK. This statistics are also shown in this window. P - Process memory (PGA) details Sometimes the Oracle processes allocate too much PGA memory. In this case it could be important to see the memory allocation size for a particular database process. This window provides such a view by using the information from the views V$PROCESS_MEMORY, V$SESSION, V$PROCESS etc. After locating an interesting process, you can press the z or Z keys to get more session details. p - Parallel execution details This windows displays the currently running parallel execution operations. It shows the coordinator process together with the parallel execution servers. The additional information to the processes are available by pressing the z or Z keys. r - RAC statistics This window shows the RAC statistics similar to the STATSPACK and AWR reports. S - SGA information This window is based on the view V$LIBRARYCACHE and displays the delta values for library cache statistics during the last refresh interval. The window header contains some statistics about the parses per second 1, 5, and 15 minutes ago. If the connected database user has got the required privilege to select from the fixed views, then this window also shows the number of library cache sub-pools using the corresponding hidden parameter _kghdsidx_count. s / ss - Top sessions views Both windows are based on the views V$SESSION and V$SESSTAT and show all available database sessions. You would use these windows to look for the active sessions, which consume a 4-29 Available performance screens

50 lot of resources (like the top utility in UNIX). The window header shows the number of all and active sessions and the statistics for the logical reads, physical reads and the physical writes during the last refresh interval. The header shows some time model statistics (DB time, DB CPU and background elapsed time) as well. The information in the header should help you to estimate the load for the whole instance before starting to look for a special session. The s window shows the database user name, session status, program and machine. (Both program and machine can be shown or be hidden using the corresponding toggle keys 7 and 8.) The ss window shows the event details from the view V$SESSION for each session. In both windows you can hide all inactive sessions by pressing the i (idle) key. After that the s window will show only the sessions in active status and the ss window will hide the sessions waiting for the wait events from the idle class. Using the i key can help you to hide many idle sessions and to see at a glance the sessions of interest. It is possible to use the order keys in these windows to sort the sessions by SID, SPID, used CPU, logical reads (default sort order), physical reads, physical writes and redo size. This should help, for instance, to look for a reading or writing sessions. After locating a specific session you would usually like to get more details on it using the static or dynamic session views (the z or Z keys). Z - Dynamic session view After locating a special database session in one of the session views (for instance, s or ss ), you could monitor the session data using dynamic session view. The session information will be changed according to the refresh interval, so that, for instance, you can see the different running SQL statements for this session with their plans etc. The session screens are similar to the static session view ( z ) (see below). Additionally the first screen shows the following statistics (delta values): used CPU time, logical reads, consistent changes, physical reads, physical writes and redo size. These numbers allow to see, how many resources the monitoring session consumes during the refresh interval. The time model statistics for this session are shown on the last screen. z - Static session view The static session view shows the complete session information for one session. Usually you would locate a session of interest in one of the sessions views (for instance, s or ss ) and then press the z key for the further details. The information on the static session view doesn't change, so that you have enough time to check all details on this session. In fact all session data are selected once after pressing the z key and will not be refreshed. If you want to see the changes in the session view, then you should use the dynamic session view ( Z ). You can press the Z key to switch to the dynamic session view from the static session view. Anytime in this window you can press the 0 (zero) key to save the whole information into a text file. This way the collected information can be analyzed later. The first screen ( 1 ) shows the session details from the view V$SESSION. If the session is 4-30 Available performance screens

51 blocked and the database has recognized it, then the blocking session information will be shown on this window. In Oracle10g some mutex wait events don't start the blocking session recognition (see the My Oracle Support document HOW TO FIND BLOCKING SESSION FOR MUTEX WAIT EVENT cursor: pin S wait on X with the Doc ID ). The blocking session recognition from this document is implemented in AMON. To highlight this, the prefix AMON will be printed near the blocking session. The second screen (the 2 key) shows the currently running SQL statement. The next screen (the 3 key) displays the current execution plan from the view V$SQL_PLAN for this statement. The 4 key shows the last waiting events from the view V$SESSION_WAIT_HISTORY and the currently running long operations from the view V$SESSION_LONGOPS. The next screen (the 5 key) shows the last entries for this session from the active session history view V$ACTIVE_SESSION_HISTORY. If this static session view was called with z key from the the session time model window ( tt ), then the last window displays the session time model statistics as well. In other cases this window is empty. t and tt - System and session time model statistics Many Oracle reports and advisories use the time model statistics to measure the tuning effects. AMON shows the corresponding statistics (delta values) from the views V$SYS_TIME_MODEL and V$SESS_TIME_MODEL on the "t" and "tt" windows. The system level statistics help to understand the accumulated time for all database operations. You should press the t key for these statistics Available performance screens

52 The most important component is the DB time statistics. The results of a tuning session can usually be measured by reducing the DB time statistics for the whole system. The session time model view (the tt window) helps to find the sessions with the most consumption of DB Time. Such sessions could be a candidate for a performance tuning. The default sort order is by DB time. You can press the "2" key to order the sessions by DB CPU statistics. (See the second line for the available keys.) The session ordering by DB CPU is the best possibility to find out the sessions, which heavily use the CPU and don't wait for any wait events. (Such sessions would have almost equal values for the statistics DB Time and DB CPU). Further session details can be discovered by pressing the z or Z keys. The time model statistics are refreshed by Oracle every 10 seconds. That's why you should consider to increase the default AMON refresh interval 10 seconds on these windows. w - Active SQL work areas This window is based on the view V$SQL_WORKAREA and displays the information about the currently used work areas for SQL cursors. Some work areas don't fit in the PGA memory and the temporary segment could be allocated from the temporary tablespace. In such a case the query performance could be worse. You can see such allocation at a glance by looking at the disk size column with non-zero values. The z key will provide you further information about the selected work area Available performance screens

53 AMON screens for ASM isntances. Key Screen description D ASM disks I/O statistics for each ASM client. d ASM disks statistics. g General information about the ASM instance. h AMON help page. L Active ASM long-running operations. m ASM instance memory overview. + Double the refresh time. - Cut by half the refresh time. D - ASM disks I/O statistics for each ASM client. (Only in Oracle11g.) Often an ASM instance contains disk groups for different database. In this case it is often important to know, which database produces the most I/O load. For instance, a database could suddenly suffer from performance problems, because the other database runs the I/O intensive operations and use the same disk group. You can see from the picture above, that two different databases (a01 and b01) are currently active on this ASM instance. The default sort order for ASM disks on this window is by physical reads. You can use the number keys (see the second line) to change another sort order. On the example above the database instance a01 produces the most read operations. The instance b01 is idle. As usually you can get the details on the highlighted ASM disk with the z key Available performance screens

54 The ASM disk group and selected ASM disk details are displayed. d - ASM disks statistics. This is a main performance window for an ASM instance. The database files in ASM that are stored in a disk group are evenly distributed to eliminate hot spots and to provide uniform performance across the disks. The performance is comparable to the performance of raw devices. Usually you would not see the big differences in performance statistics between the different ASM disks. But during I/O performance problems you need to check the performance statistics on the involved ASM disks and compare them to the numbers from the database dynamic views. By pressing the d key you can see the I/O statistics with default sort order by physical reads Available performance screens

55 You can use the number keys to change the sort order. The currently order column has got a highlighted column header. Usually you would like to see more details about the corresponding disk and the disk group. You should press the z key to get the ASM disk details window. g - General information about this ASM instance. This is a default start window for AMON on a ASM instance. It gives you an overview about the relevant ASM parameters and the existing ASM disk groups Available performance screens

56 If you use a normal or high disk group redundancy, then a disk group can tolerate a disk failure. The ASM disk group would set the corresponding disk to OFFLINE, but you would not have any interrupts in the running database. Usually the column offline disks for a disk group should be 0. If you see any other values, you need to check the ASM log files. If you use ASM for host based mirroring over different storage systems, you have to use a normal or high redundancy disk groups with 2 or 3 failure groups. Each failure group would consist of ASM disks from only one storage system. In such cases the column failure groups from the g window must show only 2 or 3 failure groups for such disk groups. The number of failure groups is usually only informative in all other configurations. L - Active ASM long-running operations. This window displays active long-running ASM operations. The typical long-running operations are automatic or manual disk group rebalancing. Below you can an example of automatic disk group rebalancing activity after adding a new disk to the existing disk group Available performance screens

57 Usually you would like to know, if some rebalancing operations are running and how long this operation will take. During this time the I/O performance could be affected. You can consider to decrease the parallel degree of the rebalancing using the POWER clause of ALTER DISKGROUP statement. m - ASM instance memory overview. The ASM instance memory allocation consists mostly of SGA and PGA. This window shows the currently allocated memory for both of them Available performance screens

58 Usually you don't need to change the default memory parameters for ASM. But you would like to know the memory requirement of this ASM instance, if you want to calculate the memory consumption for all Oracle instances running on the particular server. 5 AMON command-line options At first AMON read the environment variable AMON, so that you can set all or part of these parameters there and don t specify them for every call. -a AMON default output directory AMON writes the output files to the current directory, if this parameter isn t specified. You could use this parameter, if several DBAs share the same UNIX account to place the otuput files in your personal directory. -b {y n} Some terminal fonts don t support drawing the lines. In this case you can use the option -b n to avoid drawing the boxes around the edges of a window. The default option is -b y (displaying the lines). -c count Number of updates. If no count is specified, then the default value is infinity AMON command-line options