RECO CKPT SMON ARCH PMON RMAN DBWR

Transcription

1 Database Architecture t Architecture Topics Memory Structure Background Processes Database Accessing Database Information Starting the Database SMON PMON DBWR LGWR Parameter Database Architecture SNPn LCKn Pnnn Snnn Dnnn Large Pool Shared Pool LIB Data Dic Control System Global Area (SGA) Data CJQn Database Buffer Cache 3060student.zip Trace REDO Log QMNn REDO Log Cache Alert Log RECO CKPT ARCH RMAN Archived Required Background Processes SMON PMON DBWR LGWR Large Pool Database Instance Less Common Background Processes SNPn LCKn Pnnn Snnn Dnnn CJQn QMNn Shared Pool LIB Holds Parsed SQL. Data Dic System Global Area (SGA) Holds Recent Data Dictionary Information. Shared Server Session Memory. Database Buffer Cache Holds Data Read Into Memory and Modified Data. REDO Log Cache Holds transaction data to recover from failure. Commonly Used Background Processes RECO CKPT ARCH 1

2 DATABASE BUFFER CACHE REDO LOG BUFFER LIBRARY CACHE DATA DICTIONARY CACHE LARGE POOL Memory Allocations The Database Buffer Cache is where the data retrieved by an SQL statement are stored As changes are made to the database, Oracle records them in a transaction log. This transaction information is initially stored in the Redo Log Buffer. When a user issues a SELECT statement, Oracle parses the statement and produces an execution plan for retrieving the data. Oracle saves the parsed SQL statements and execution plans in the Library Cache and will reuse these if possible The Data Dictionary Cache stores data on recently accessed data dictionary information such as column names and passwords. Used as session memory for shared server connections, memory storage for backup processes, and memory storage for parallel processing. Background Processes What are BG Processes Background processes are a collection of programs that run on the database server and each process is assigned a specific task. Background process may be required or optional Background Processes Required DBWR LGWR SMON PMON Also Running CKPT RECO CJQ Unnecessary. May be shut down QMN Process to be Started Later ARCH 2

3 SMON The System Monitor process performs the following functions: Performs automatic ti instance recovery Reclaims space used by temporary segments no longer in use Merges contiguous areas of free space in the datafiles PMON The Process Monitor performs the following functions: Cleans up abnormally terminated connections Rolls back uncommitted transactions Releases locks held by a terminated process Frees SGA resources allocated to the failed process Restarts failed shared server and dispatcher processes DBWR & LGWR DBWR copies the data in the dirty buffers to the data files. More than one DBWR process can exist. The LGWR process writes the contents of the Redo Buffer Cache to a file. CKPT The Checkpoint Process (CKPT) reconciles the data in the Database Buffer Cache and updates the headers in the data files to reflect the checkpoint. It also signals DBWR to flush the dirty buffers in the Database Buffer Cache to the data files. A Checkpoint occurs whenever: The currently active REDO Log File is filled (there is an automatic log file switch). The DBA forces a log file switch. A log_checkpoint_interval has been reached. A log_checkpoint_timeout has been reached. 3

4 Log Checkpoint Interval and Time Out. Add (or modify) the following lines to the PFile (You don t need to add the comments). log_checkpoint_interval = log_checkpoint_timeout = 1800 # a CKPT will occur # after this many # O/S BLOCKS have been # written to the # Redo Log File. # a CKPT will occur # if no CKPT has # happened after this # many seconds have # passed, To disable, # set to zero. ARCH Whenever a Redo Log File switch occurs, ARCH will make a copy of the filled Redo Log file in a designated directory. For ARCH to copy the Redo Log : The database must be in archivelog mode. A valid destination must be specified in the PFile or SPFile. The destination directory must have permissions that make it accessible to the database. Listener The Listener Process has the following characteristics: It listens for client requests and establishes a connection with the server. It directs the queries to a function that either creates a dedicated connection for each user (old) or to a multithreaded server (shared server) process (new) that handles many users. The listener serves only to establish a connection between the client and the server. Once it establishes the connection, it has no other purpose. Other Processes Recoverer (RECO) is only used with a distributed database and it attempts to resolve a transaction when one of the servers on the distributed database fails. Snapshot (SNPn SNPn) refreshes internal job queues. Lock (LCKn LCKn) is used for more complex locking of multiple servers when a parallel system is used. Dispatcher (Dnnn Dnnn) is used to handle multiple connections with multiple protocols. Server (Snnn Snnn) manages multiple connections when a dedicated server is used. 4

5 Other Processes (cont.) Parallel Query Server (Pnnn) allows a single query s resource allocation to be allocated among multiple servers. Coordinator Job Queue (CJQn CJQn) handles automated t jobs submitted with the DBMS_JOBS package. Turn it off by setting JOB_QUEUE_PROCESSES=0 in the Pfile. Queue Monitor (QMNn) allows you to monitor messages in queues. Turn it off by setting AQ_TM_PROCESSES=0 in the Pfile. Viewing Active Processes SQL> select program from v$session; PROGRAM oracle@clem.mscd.edu (PMON) oracle@clem.mscd.edu l d (DBW0) oracle@clem.mscd.edu (LGWR) oracle@clem.mscd.edu (CKPT) oracle@clem.mscd.edu (SMON) oracle@clem.mscd.edu (RECO) oracle@clem.mscd.edu (CJQ0) These process may be shut down. oracle@clem.mscd.edu (QMN0) sqlplus@clem.mscd.edu (TNS V1-V3) Connected user Utility Programs Oracle offers several Utility Programs that perform specific tasks. These Utility Programs are run from the operating system and connect to the database (much like SQL*Plus). Examples of some Utility Programs are listed below. Recovery Manager (RMAN) automates backup and recovery procedures. Export/Import (Exp/Imp) allows the user to save selected database objects to a file and later import those objects. SQL*Loader will load data from a system file into tables in the database. Database 5

6 REDO Log File Usage Multiplexed REDO Log Group 1 Group 2 Group 3 Disk 1 Logfile Member Logfile Member Logfile Member Log File 1 Log File 2 Log File 3 Disk 2 Logfile Member Logfile Member Logfile Member Init.ora Spfile.ora Parameter The init.ora file contains the parameters and parameter values set for the database. You can edit this file and change the parameters. This file may be read when the database is started. This file contains the same parameter values as is found in the init.ora. You cannot edit this file. You can change it while the database is running using the ALTER SYSTEM command. Control store information about the database that can be used to recreate the structure of the database in case of a catastrophic failure. contain a record of the file names and locations of the Data and Redo Log files. If a new database file is added to the database, the control file is dynamically updated. multiple copies of the control file are usually defined and automatically maintained by Oracle. The control file(s) are identified in the init.ora file 6

7 Creating New Control Shutdown the database. Use the OS to make copies of the existing control file giving each copy a new name. Use the OS to move the copied control files to the new locations. Edit the init.ora file and add the fully qualified path names to the highlighted line shown below. Separate each name with a comma. Startup the database. # File Configuration control_files=/ =/oraclec/data/db08/disk1/control.ctl Data Data files contain the actual data from tables, indexes, etc, and the definitions of objects such as views and synonyms. The data files also contain the data from the data dictionary and the rollback segments. Database Storage Structures Object Tablespace Segement Extent DB Block Description Largest storage unit where tables, indexes, etc. are stored. Similar to a folder in MS Windows. A database object that stores data. Examples are Tables, Indexes, Temporary, and UNDO segments. Each segment is comprised of one or more extents. Using multiple extents allows the database to grow in a controlled manner. The smallest storage unit. Each extent is comprised of one or more contiguous DB Blocks (DB Block size is 8k in our databases). Note that the blocks forming an extent must be contiguous but different extents may be physically located in different parts of the disk. Physical and Logical Structures Physical Structures Operating System Operating System Blocks Logical Structures Database Tablespaces Segments Extents Contiguous Data Blocks 7

8 Assignment of Data Tablespace 1 (SYSTEM) Tablespace 2 (INDEXES) Tablespace 3 (DATA) Alert Log Alert Log and Trace Records events such as database startup and shutdown, log file switches, and creation of new tablespaces and/or datafiles. Records certain system error messages that are generally recorded with an entry beginning with ORA-. owned by SYSTEM File owned by INDEXES owned by DATA Trace are diagnostic files generated by errors in certain processes. Trace files are given names with an extension of.trc. Accessing Database Information Default User Names Oracle provides several user accounts when the database is first installed. The accounts (with their passwords) shown below are of particular importance. SYS change_on_install SYSTEM change_on_install The most important user as it owns most of the tables, functions, and procedures of the database. SYS also owns most of the predefined system views into the data dictionary. Granted permission on most of the views owned by SYS. 8

9 Table Name Aud$ Clu$ Col$ Con$ File$ Snap$ Tab$ Database Core Tables (Ends with a $ and owned by SYS) Contents Stores information generated from the audits imposed. Contains information of clusters Contains information on table columns. Constraints information on constraints Contains information on the files owned by the database Contains information on snapshots Contains information on tables. Naming Convention for Data Dictionary Views Oracle names permanent data dictionary views using a prefix. The prefix describes what information the view returns. USER ALL DBA Returns objects owned by the logged User. Returns objects the logged the logged in user has access to. Returns all objects owned by all users. Important Data Dictionary Views Select From USER_TABLES ALL_TABLES DBA_TABLES USER_USER DBA_USER Returns Information On All tables the user owns. All tables the users can access including tables the user owns. All of the tables the database owns regardless of schema. The user s account. The accounts of all users on the database. Dynamic Performance Tables and Views Dynamic performance tables are created in memory when the database is started. These tables exist only in memory and their values are lost when the database is shut down. Dynamic performance table names begin with x$. Dynamic performance views are views that access dynamic performance tables and their names begin with v$. 9

10 Important Dynamic Performance Views Select From V$SESSION V$SYSSTAT V$ROLLSTAT V$LOGFILE V$SGA Returns Information On Users who are currently connected to the database. Many database performance statistics. Rollback segments. Redo log files. Memory allocations of the SGA. V$PARAMETER The current values of all database parameters. This is one of the most useful views. You can also view this information by entering show parameters at the SQL prompt. V$SPPARAMETER Shows the settings in the active SPFile. Starting the Database Connecting to Your Database You will be assigned a database number between 1 and 8. Your database SID will be DB0x where x is replaced by your number. Follow the instructions at the SQL link on this site to set up your rascal account. Log onto rascal and enter your DB0x Last login: Tue Jan 25 08:06: from hlrn.qwest.net SIDS on this machine are DB00 DB01 DB02 DB03 DB04 DB05 DB06 DB07 DB08 DBinst ORACLE_SID = [garmang]? Access the Database After you log onto rascal, enter the following SQL> connect sys/change_on_install as sysdba One of the following responses will occur. Connected Connected to an idle instance. If the databasse is not running, start it with the command below. SQL> startup The database is running. Indicates the database is not running 10

11 Startup the Database SQL> startup Starts the Database ORACLE instance started. Total System Global Area bytes Fixed Size bytes Variable Size bytes Database Buffers bytes Redo Buffers bytes Database mounted. Database opened. You can connect to other SQL> connect system/change_on_install users once the database has Connected. been started. SQL> show user USER is "SYSTEM" SQL> The database will remain running until someone issues the shutdown command. It will remain running even after you log off of the operating system. Startup Startup Mount Database Startup Options Startup Nomount Startup Restrict Startup Recover Startup Force Starts the database instance and background processes. Opens the database. Starts the instance and attaches the database, but does not open it. Allocates the memory and starts the background processes but does not attach the database. Mounts and opens the database but allows only those users with the restricted session privilege to access it. The instance is started but the database remains closed as recovery takes place. Should be used to start the database only after all attempts to shutdown and restart the database have failed. PFile (initdb0x.ora) InitDB0x.ora contains the parameter values the database may use when it is started. Parameters are modified by editing i the file and changing the values. The following slide shows the (partial) contents of a PFile. ############################# # Copyright (c) 1991, 2001, 2002 by Oracle Corporation ############################# # Cache and I/O db_block_size=8192 db_cache_size= db_file_multiblock_read_count=16 # Cursors and Library Cache open_cursors=300 # Database Identification db_domain="mscd.edu" db_name=db08 11

12 PFile Parameters Parameters in the PFile may be modified when the database is shut down. Edit the PFile with a text editor such as pico or vi. If a parameter is not specified in the PFile, you can add the parameter to the file and assign it a value. Some Important PFile Parameters Paramter db_cache_size shared_pool_size db_files remote_login _passwordfile spfile resource_limit Domain Number Number Number Description Number of buffers of size db_block_size allocated to the database buffer cache. Memory (in bytes) allocated to the shared pool. Maximum number of files that may be opened. None, Exclusive, Allows users to be authenticated by Internal, Shared accounts listed in a file. Exclusive means the file is used exclusively by one database. Shared means the file is used by more than one database. String True, False Name of the SPFile the database should use. Must be set to TRUE if Profiles are used. spfiledb0x.ora Contents of the file set the same parameter values as the initdb0x.ora file. Parameters in the file can be modified by the ALTER SYSTEM command the file should not be edited. View the current setting of the file using the following command: SQL> SELECT NAME, VALUE FROM V$SPPARAMETER; Changing the Value of Parameters in the SPFile Alter System Set <Parameter> = <Value> Scope = <Memory SPFile Both>; A parameter value may be changed temporarily by setting the Scope = Memory. A parameter value may be changed in the SPFile by setting the Scope = SPFile. The change will not take affect until the database is started again. A parameter may be changed immediately and in the SPFile by setting Scope = Both. Not all parameters may be set or changed using Alter System. 12

13 Examples of Alter System SQL> Alter System set Open_Cursors = Scope = Memory; SQL> Alter System set db_files = Scope = SPFile; SQL> Alter System set 2 log_checkpoint_interval = 60 3 Scope = Both; PFile & SPFile At Database Startup Oracle will use the parameter values in the SPFile if the file is found. Oracle will use the parameter values in the PFile if the SPFile doesn t exist. The parameter values in the PFile and the SPFile will generally be different. Creating SP from Pfiles To Create an SPFile from a PFile: Creating P from SPfiles To Create a PFile from an SPFile: SQL> Connect / As Sysdba SQL> Shutdown SQL> Create SPFile = '/oraclec/920/dbs/spfiledb08.ora' /920/db / ' 2 From PFile = '/oraclec/920/dbs/initdb08.ora'; SQL> Startup The SPFile for DB08 is recompiled with the parameter values in initdb08.ora. SQL> Connect / As Sysdba SQL> Shutdown SQL> Create PFile = '/oraclec/920/dbs/initdb08.ora' /920/db /i itdb08 ' 2 From SPFile = '/oraclec/920/dbs/spfiledb08.ora'; SQL> Startup The PFile for DB08 is recreated with the parameter values in SPFileDB08.ora. 13

14 Viewing the Values of the Parameters To view the settings in the PFile, edit the file with a text editor (vi, nano, or pico) To view the settings in the SPFile, enter the following while logged onto SYS: SQL> SELECT NAME, VALUE FROM V$SPPARAMETER; To view the settings currently being used by the database, enter the following while logged onto SYS: SQL> SHOW PARAMETERS Viewing Specific Parameters To view specific database parameters, enter show followed by the name of the parameter: SQL> show parameter db_block_size SQL> show parameter SPFile - will return a filename if an SPFile is in use. To view the parameters of a database area, enter show followed by the name of the area. SQL> show parameter audit SQL> show parameter files Shutting Down the Database [27]> dba You can use sqlplus /nolog instead ORACLE_BASE /oraclec ORACLE_HOME /oraclec/920 OEACLE_DOC /oraclec/920/doc ORACLE_SID DB08 PATH.:/oraclec/920/bin:/usr/bin:/etc:/usr/sbin:/usr/bin/X11:/usr/local/ bin DISPLAY mscd0433.client.mscd.edu:0.0 SQL*Plus: Release Production on Fri Dec 16 23:00: Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved. SQL> connect / as sysdba Connect to the SYS account Connected. Indicates the database is running SQL> shutdown Shut down the database Database closed. Database dismounted. ORACLE instance shut down. Database Shutdown Options Shutdown Oracle waits for all transactions to complete and for all connected users to exit oracle before shutting down. Shutdown Transactional Oracle waits for users to complete their current transactions before shutting down and currently connected users will not be allowed to start new transactions Shutdown immediate Oracle will rollback all currently uncommitted transactions and then shut down the database. Shutdown Abort Uncommitted transactions are not rolled back and currently logged in users are immediately disconnected from the database. 14