These copies should be placed on different disks, if possible. Disk 1 Disk 2 Disk 3

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1 DATABASE CONFIGURATIONS Configuration Topics Simple Databases with Mirroring Multiplexing Control Files and REDO Logs Disk Shadowing Database Links and Snapshots Optimal Flexible Architecture 1

2 Stand Alone Host The SGA contains all of the memory allocations including the Database Buffer Cache, the REDO Log Buffer Cache, and the Shared Pool. The Background Process include SMON, PMON, DBWR, LGWR, etc. The Database Files include Data Files, Control Files, REDO Log Files, etc. SGA Background Processes Database Files Stand Alone Host With Mirroring The database can maintain synchronized copies of the Control File and the REDO Log Files. These copies should be placed on different disks, if possible. REDO Log & Control Files SGA Background Processes Copies of REDO Log & Control Files Copies of REDO Log & Control Files Disk 1 Disk 2 Disk 3 2

3 Multiplexing the Control File Oracle allows you to maintain two or more synchronized copies of the Control File. You can always reconstruct the structure of the database as long as you can retrieve one of these control file. You should locate the control files on different disks, if possible. Following are the steps necessary to multiplex the Control File. Shutdown the Database. Copy the Control File and Rename the Copy (or Copies). Move the Control File(s) to the new location(s). Edit the initdb0x.ora File and add the new Control File(s) to the init it file. Connect to the SYS user. Create the SPFile from the PFile. Startup the Database. Adding a Second Control File Copy the Control File to disk 2 and rename it. [21]> cd /oraclec/data/db08/disk2 [22]> cp /oraclec/data/db08/disk1/control.ctl. [23]> mv control.ctl tl control1.ctl tl Edit initdb08.ora and find the lines shown. ########################################### # File Configuration ########################################### control_files=/ =/oraclec/data/db08/disk1/control.ctl Add the location of the new Control File separating the names with a comma. ########################################### # File Configuration ########################################### control_files=(/oraclec/data/db08/disk1/control.ctl, /oraclec/data/db08/disk2/control1.ctl) 3

4 Adding a Second Control File (cont) SQL> connect sys/change_on_install as sysdba Connected. SQL> create spfile = '/oraclec/11g/dbs/spfiledb08.ora' 2 from pfile = '/oraclec oraclec/11g/ /11g/dbs dbs/initdb08.ora ora'; File created. Startup the database and enter the command below to see that the second Control File has been identified by the database. SQL> show parameter control_file NAME TYPE VALUE control_file_record_keep_time integer 7 control_files string /oraclec/data/db08/ Disk1/control.ctl, /oraclec/data/db08 /Disk2/control1.ctl Multiplexing The REDO Log Files Log File GROUPS Ad database must have at least two Log File Groups. These Groups are used in a circular fashion meaning that when the last Group is full, the data in the first Group will be overwritten. Log File MEMBERS Each Redo Log file in a Group is called a Member. Each member of the group is update simultaneously so that all members contain identical data. 4

5 REDO Groups and Members Group 1 Group 2 Group 3 Disk 1 G1 M1 Member G2 M1 Member G3 M1 Member Disk 2 G1 M2 Member G2 M2 Member G3 M2 Member Existing Log File Groups SQL> connect sys/change_on_install as sysdba Connected. SQL> Select * From v$logfile; GROUP# STATUS TYPE MEMBER ONLINE /oraclec/data/db08/disk1/redo01.log 2 ONLINE /oraclec/data/db08/disk1/redo02.log 3 ONLINE /oraclec/data/db08/disk1/redo03.log The database initially has three REDO Log Files which are used in a circular fashion. There is no multiplexing (redundancy) of the REDO data. 5

6 Creating a New Log File Group SQL> Alter Database ADD Logfile Group 4 2 ('/oraclec/data/db08/disk1/redo04.log') 3 Size 2M; Database altered. A new Group (Group 4) has been created with one member. Subsequent members will need a file name and the file size will always be 2M in this example. SQL> Select * From v$logfile; GROUP# STATUS TYPE MEMBER ONLINE /oraclec/data/db08/disk1/redo01.log 2 ONLINE /oraclec/data/db08/disk1/redo02.log 3 ONLINE /oraclec/data/db08/disk1/redo03.log 4 ONLINE /oraclec/data/db08/disk1/redo04.log Adding Log File Members to a Group SQL> Alter Database ADD Logfile Member 2 '/oraclec oraclec/data/db08/disk2/redo01_2.log 2 To Group 1; Database altered. SQL> Alter Database ADD LogFile Member 2 '/oraclec/data/db08/disk2/redo02_2.log To Group 2; Database altered. SQL> Alter Database ADD Logfile Member 2 '/oraclec oraclec/data/db08/disk2/redo03 / / / _ 2.log To Group 3; Database altered. SQL> Alter Database ADD Logfile Member 2 '/oraclec/data/db08/disk2/redo04_2.log' To Group 4; Database altered. 6

7 New Log File Groups SQL> select a.group#,member,members, 2 archived,b.status,first, _ time 3 from v$logfile a,v$log b 4 where a.group# = b.group#; GROUP# MEMBERS M ARC STATUS FIRST_TIM /oraclec/data/db08/disk1/redo01.log 2 NO CURRENT 17-DEC-10 1 /oraclec/data/db08/disk2/redo01 / / / / _ 2.log 2 NO CURRENT 17-DEC-10 2 /oraclec/data/db08/disk1/redo02.log 2 YES INACTIVE 14-DEC-10 2 /oraclec/data/db08/disk2/redo02_2.log 2 YES INACTIVE 14-DEC-10 3 /oraclec/data/db08/disk1/redo03.log 2 YES INACTIVE 14-DEC-10 3 /oraclec/data/db08/disk2/redo03_2.log 2 YES INACTIVE 14-DEC-10 4 /oraclec/data/db08/disk1/redo04.log 2 YES UNUSED 4 /oraclec/data/db08/disk2/redo04_2.log 2 YES UNUSED 8 rows selected. Stand Alone Host With Disk Shadowing The Operating System may be used to maintain synchronized copies of the database s DATA Files. The DBMS cannot maintain these copies. Usually a version of RAID (usually RAID 5) must be implemented to accomplish shadowing. Drive 1 Drive 2 SGA Background Processes Database Files Database Files Operating System Copies Files From Array 1 To Array 2 Backup Protection Better Performance Copies of Database Files Copies of Database Files Disk Array 1 Disk Array 2 7

8 Database Links Database Link Requirements A Database Link is an Oracle object that allows you to access tables on a remote database. To create a database link, you must know the following: A valid account (account name and password) on the remote database The Host String, or identifier, on the remote database. (student@clem.mscd.edu for Metro) 8

9 Database Link Structure The following statement t t creates the Database Link object. The PUBLIC keyword gives all users permission to access the remote database through the link. If omitted, only the owner of the link can use it. CREATE [PUBLIC] DATABASE LINK link_namename CONNECT TO remote_userid IDENTIFIED BY remote_password USING host_string ; Database Link Example SQL> CREATE DATABASE LINK Customer_Link 2 CONNECT TO smith 3 IDENTIFIED BY welcome 4 USING remote123.world ; Database link created. The above command creates a Database Link object named Customer_Link. It accesses a database named remote123.world as user smith with a password of welcome. 9

10 Accessing Data Through the Database Link The following table retrieves the all of the data from the Customer table owned by smith on the remote database. SQL> SELECT * FROM SQL> CREATE VIEW Cust AS SELECT * FROM Customer@Customer_Link; SQL> CREATE SYNONYM Cust FOR Customer@Customer_Link; By placing the database link in a VIEW or a SYNONYM as shown above, the link can be hidden from the user. Once the view is contained in the VIEW or SYNONYN object, the user only needs to enter the command below: SQL> SELECT * FROM Cust; Snapshots (Materialized Views) Snapshots are read only views that extract data from other segments (Tables or Views). Snapshots are created with a defining query in a manner similar to creating a View. Snapshots are updated automatically at intervals established in the definition of the Snapshot. 10

11 Attempting to Create the Snapshot SQL> connect sys/change_on_install as sysdba From SYS grant Connected. the CREATE SQL> Grant Create Snapshot to JERRY; SNAPSHOT privilege to Grant succeeded. JERRY. SQL> Connect JERRY/Welcome Log onto Connected. JERRY s account SQL> Create Snapshot CUST_SHOT 2 REFRESH START WITH Sysdate NEXT Sysdate + 1/24 3 AS Select * From CUSTOMER; AS Select * From CUSTOMER The Table Must Have a Primary Key. * ERROR at line 3: ORA-12014: table 'CUSTOMER' does not contain a primary key constraint Creating the Snapshot SQL> Alter Table Customer 2 ADD Constraint CID_PK Primary Key (CID); Table altered. SQL> Create Snapshot CUST_SHOT 2 REFRESH START WITH Sysdate NEXT Sysdate + 1/24 3 AS Select * From Customer; Materialized view created. Add the Primary Key to Customer. The Snapshot will be created and populate immediately (SYSDATE) and updated every hour (SYSDATE + 1/24). 11

12 Attempting to Modify Data in a Snapshot SQL> Insert Into CUST_SHOT Values 2 (10, 'Flanders', 'W', 'A2'); Insert Into CUST_SHOT SHOT Values * ERROR at line 1: ORA-01732: data manipulation operation not legal on this view SQL> Update CUST_SHOT 2 Set Region = 'E'; Update CUST_SHOT * ERROR at line 1: ORA-01732: data manipulation operation not legal on this view All attempts to modify the data in a snapshot will fail. Snapshot and Database Link Snapshots are frequently used to retrieve data from remote databases using a database link. In the example below, a snapshot is created that accesses the data from the Customer table on the remote database. The snapshot is refreshed every thirty minutes. This technique is useful if the organization can afford to use data that is (at most) thirty minutes out of date. SQL> Create Snapshot Customer_Shot 2 REFRESH START WITH Sysdate 3 NEXT Sysdate + 30/ AS SELECT * FROM Customer@Customer_Link; 12

13 Optimal Flexible Architecture The OFA standard is a set of configuration guidelines created to ensure fast, reliable Oracle databases that require little maintenance (Oracle9i Administrator's s Reference). OFA benefits include: Organize large amounts of complicated software and data on disk, to avoid device bottlenecks and poor performance. Facilitate routine administrative tasks such as software and data backup, which are often vulnerable to data corruption. Facilitate switching between multiple l Oracle databases. Adequately manage and administer database growth. Help eliminate fragmentation of free space in the data dictionary, isolate other fragmentation, and minimize resource contention. OFA Standards OFA places standards on the following: Naming conventions for files and directories. Creating a structured directory tree. Creating specific paths to files designed to store specific data. Separates tablespace content to minimize fragmentation, minimize I/O request contention, and facilitate administrative flexibility. 13

14 OFA Compliant Tablespaces Tablespace Name SYSTEM Contents Data Dictionary Tables. System UNDO Segment. Cannot be taken offline for maintenance. Required. Created and maintained by the DBMS. SYSAUX An auxiliary tablespace to SYSTEM. SYSAUX contains segments and data that were contained in SYSTEM in previous versions of Oracle. SYSAUX contains noncritical information thus the database can continue to function if SYSAUX fails. TOOLS Tools created by the DBA's/Users.3rd Party Vendor Tools. OFA Compliant Tablespaces (cont.) Tablespace Name UNDOTBS TEMP USERS Contents All UNDO except for the System UNDO Segment. (High Volume. Usually managed by the DBMS) May be taken offline by the DBA for mainenance. Required. The Tablespace is created with special commands. Temporarily stores created objects such as large sorted tables that require large storage. Used dby the System and by Users. Required. The Tablespace is created with special commands. Application Tables and Clusters. (High volume, usually highly fragmented) 14