Creating a Physical Standby Database
Preparing the Primary Database for Standby Database Creation Before you create a standby database you must first ensure the primary database is properly configured.
Enable Forced Logging
Place the primary database in FORCE LOGGING mode after database creation using the following SQL statement: SQL> ALTER DATABASE FORCE LOGGING;
This statement can take a considerable amount of time to complete, because it waits for all unlogged direct write I/O to finish.
Create a Password File
Create a password file if one does not already exist. Every database in a Data Guard configuration must use a password file, and the password for the SYS user must be identical on every system for redo data transmission to succeed.
Configure a Standby Redo Log
A standby redo log is required for the maximum protection and maximum availability modes and the LGWR ASYNC transport mode is recommended for all databases. Data Guard can recover and apply more redo data from a standby redo log than from archived redo log files alone. You should plan the standby redo log configuration and create all required log groups and group members when you create the standby database. For increased availability, consider multiplexing the standby redo log files, similar to the way that online redo log files are multiplexed.
Perform the following steps to configure the standby redo log.
Step 1 Ensure log file sizes are identical on the primary and standby databases.
The size of the current standby redo log files must exactly match the size of the current primary database online redo log files. For example, if the primary database uses two online redo log groups whose log files are 200K, then the standby redo log groups should also have log file sizes of 200K.
Step 2 Determine the appropriate number of standby redo log file groups. Minimally, the configuration should have one more standby redo log file group than the number of online redo log file groups on the primary database. However, the recommended number of standby redo log file groups is dependent on the number of threads on the primary database. Use the following equation to determine an appropriate number of standby redo log file groups:
(maximum number of logfiles for each thread + 1) * maximum number of threads
Using this equation reduces the likelihood that the primary instance's log writer (LGWR) process will be blocked because a standby redo log file cannot be allocated on the standby database. For example, if the primary database has 2 log files for each thread and 2 threads, then 6 standby redo log file groups are needed on the standby database.
Note:
Logical standby databases may require more standby redo log files (or additional ARCn processes) depending on the workload. This is because logical standby databases also write to online redo log files, which take precedence over standby redo log files. Thus, the standby redo log files may not be archived as quickly as the online redo log files.
Step 3 Verify related database parameters and settings.
Verify the values used for the MAXLOGFILES and MAXLOGMEMBERS clauses on the SQL CREATE DATABASE statement will not limit the number of standby redo log file groups and members that you can add. The only way to override the limits specified by the MAXLOGFILES and MAXLOGMEMBERS clauses is to re-create the primary database or control file.
Step 4 Create standby redo log file groups. To create new standby redo log file groups and members, you must have the ALTER DATABASE system privilege. The standby database begins using the newly created standby redo data the next time there is a log switch on the primary database. Example 3-1 and Example 3-2 show how to create a new standby redo log file group using the ALTER DATABASE statement with variations of the ADD STANDBY LOGFILE GROUP clause. Example 3-1 Adding a Standby Redo Log File Group to a Specific Thread The following statement adds a new standby redo log file group to a standby database and assigns it to THREAD 5: SQL> ALTER DATABASE ADD STANDBY LOGFILE THREAD 5
2> ('/oracle/dbs/log1c.rdo','/oracle/dbs/log2c.rdo') SIZE 500M;The THREAD clause is required only if you want to add one or more standby redo log file groups to a specific primary database thread. If you do not include the THREAD clause and the configuration uses Real Application Clusters (RAC), Data Guard will automatically assign standby redo log file groups to threads at runtime as they are needed by the various RAC instances. Example 3-2 Adding a Standby Redo Log File Group to a Specific Group Number You can also specify a number that identifies the group using the GROUP clause: SQL> ALTER DATABASE ADD STANDBY LOGFILE GROUP 10
2> ('/oracle/dbs/log1c.rdo','/oracle/dbs/log2c.rdo') SIZE 500M;Using group numbers can make administering standby redo log file groups easier. However, the group number must be between 1 and the value of the MAXLOGFILES clause. Do not skip log file group numbers (that is, do not number groups 10, 20, 30, and so on), or you will use additional space in the standby database control file.
Note:
Although the standby redo log is only used when the database is running in the standby role, Oracle recommends that you create a standby redo log on the primary database so that the primary database can switch over quickly to the standby role without the need for additional DBA intervention. Consider using Oracle Enterprise Manager to automatically configure standby redo log on both your primary and standby databases.
Step 5 Verify the standby redo log file groups were created. To verify the standby redo log file groups are created and running correctly, invoke a log switch on the primary database, and then query either the V$STANDBY_LOG view or the V$LOGFILE view on the standby database once it has been created. For example:
SQL> SELECT GROUP#,THREAD#,SEQUENCE#,ARCHIVED,STATUS FROM V$STANDBY_LOG;
GROUP# THREAD# SEQUENCE# ARC STATUS
---------- ---------- ---------- --- ----------
3 1 16 NO ACTIVE
4 0 0 YES UNASSIGNED
5 0 0 YES UNASSIGNED
Set Primary Database Initialization Parameters
On the primary database, you define initialization parameters that control redo transport services while the database is in the primary role. There are additional parameters you need to add that control the receipt of the redo data and log apply services when the primary database is transitioned to the standby role.
Example 3-3 shows the primary role initialization parameters that you maintain on the primary database. This example represents a Data Guard configuration with a primary database located in Chicago and one physical standby database located in Boston. The parameters shown in Example 3-3 are valid for the Chicago database when it is running in either the primary or the standby database role. The configuration examples use the names shown in the following table:
Database | | Oracle Net Service Name |
Primary | chicago | chicago |
Physical standby | boston | boston |
Example 3-3 Primary Database: Primary Role Initialization Parameters
DB_NAME=chicago
DB_UNIQUE_NAME=chicago
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston)'
CONTROL_FILES='/arch1/chicago/control1.ctl', '/arch2/chicago/control2.ctl'
LOG_ARCHIVE_DEST_1=
'LOCATION=/arch1/chicago/
VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
DB_UNIQUE_NAME=chicago'
LOG_ARCHIVE_DEST_2=
'SERVICE=boston LGWR ASYNC
VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)
DB_UNIQUE_NAME=boston'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_STATE_2=ENABLE
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_FORMAT=%t_%s_%r.arc
LOG_ARCHIVE_MAX_PROCESSES=30
These parameters control how redo transport services transmit redo data to the standby system and the archiving of redo data on the local file system. Note that the example specifies the LGWR process and asynchronous (ASYNC) network transmission to transmit redo data on the LOG_ARCHIVE_DEST_2 initialization parameter. These are the recommended settings and require standby redo log files
Example 3-4 shows the additional standby role initialization parameters on the primary database. These parameters take effect when the primary database is transitioned to the standby role. Example 3-4 Primary Database: Standby Role Initialization Parameters FAL_SERVER=boston
FAL_CLIENT=chicago
DB_FILE_NAME_CONVERT='boston','chicago'
LOG_FILE_NAME_CONVERT=
'/arch1/boston/','/arch1/chicago/','/arch2/boston/','/arch2/chicago/'
STANDBY_FILE_MANAGEMENT=AUTO
Specifying the initialization parameters shown in Example 3-4 sets up the primary database to resolve gaps, converts new datafile and log file path names from a new primary database, and archives the incoming redo data when this database is in the standby role. With the initialization parameters for both the primary and standby roles set as described, none of the parameters need to change after a role transition. The following table provides a brief explanation about each parameter setting shown in Example 3-3 and Example 3-4.
Parameter | Recommended Setting |
| Specify an 8-character name. Use the same name for all standby databases. |
| Specify a unique name for each database. This name stays with the database and does not change, even if the primary and standby databases reverse roles. |
| Specify the DG_CONFIG attribute on this parameter to list the DB_UNIQUE_NAME of the primary and standby databases in the Data Guard configuration; this enables the dynamic addition of a standby database to a Data Guard configuration that has a Real Application Clusters primary database running in either maximum protection or maximum availability mode. By default, the LOG_ARCHIVE_CONFIG parameter enables the database to send and receive redo; after a role transition, you may need to specify these settings again using the SEND, NOSEND, RECEIVE, or NORECEIVE keywords. |
| Specify the path name for the control files on the primary database. Example 3-3 shows how to do this for two control files. It is recommended that a second copy of the control file is available so an instance can be easily restarted after copying the good control file to the location of the bad control file. |
| Specify where the redo data is to be archived on the primary and standby systems. In Example 3-3: · LOG_ARCHIVE_DEST_1 archives redo data generated by the primary database from the local online redo log files to the local archived redo log files in /arch1/chicago/. · LOG_ARCHIVE_DEST_2 is valid only for the primary role. This destination transmits redo data to the remote physical standby destination boston. Note: If a flash recovery area was configured (with the DB_RECOVERY_FILE_DEST initialization parameter) and you have not explicitly configured a local archiving destination with the LOCATION attribute, Data Guard automatically uses the LOG_ARCHIVE_DEST_10 initialization parameter as the default destination for local archiving. See Section 5.2.3 for more information. Also, see Chapter 14 for complete LOG_ARCHIVE_DEST_n information. |
| Specify ENABLE to allow redo transport services to transmit redo data to the specified destination. |
| Set the same password for SYS on both the primary and standby databases. The recommended setting is either EXCLUSIVE or SHARED. |
| Specify the format for the archived redo log files using a thread (%t), sequence number (%s), and resetlogs ID (%r). See Section 5.7.1 for another example. |
| Specify the maximum number (from 1 to 30) of archiver (ARCn) processes you want Oracle software to invoke initially. The default value is 4. See Section 5.3.1.2 for more information about ARCn processing. |
| Specify the Oracle Net service name of the FAL server (typically this is the database running in the primary role). When the Chicago database is running in the standby role, it uses the Boston database as the FAL server from which to fetch (request) missing archived redo log files if Boston is unable to automatically send the missing log files. See Section 5.8. |
| Specify the Oracle Net service name of the Chicago database. The FAL server (Boston) copies missing archived redo log files to the Chicago standby database. See Section 5.8. |
| Specify the path name and filename location of the primary database datafiles followed by the standby location. This parameter converts the path names of the primary database datafiles to the standby datafile path names. If the standby database is on the same system as the primary database or if the directory structure where the datafiles are located on the standby site is different from the primary site, then this parameter is required. Note that this parameter is used only to convert path names for physical standby databases. Multiple pairs of paths may be specified by this parameter. |
| Specify the location of the primary database online redo log files followed by the standby location. This parameter converts the path names of the primary database log files to the path names on the standby database. If the standby database is on the same system as the primary database or if the directory structure where the log files are located on the standby system is different from the primary system, then this parameter is required. Multiple pairs of paths may be specified by this parameter. |
| Set to AUTO so when datafiles are added to or dropped from the primary database, corresponding changes are made automatically to the standby database. |
Caution:
Review the initialization parameter file for additional parameters that may need to be modified. For example, you may need to modify the dump destination parameters (BACKGROUND_DUMP_DEST, CORE_DUMP_DEST, USER_DUMP_DEST) if the directory location on the standby database is different from those specified on the primary database. In addition, you may have to create directories on the standby system if they do not already exist. 3.1.5 Enable Archiving
If archiving is not enabled, issue the following statements to put the primary database in ARCHIVELOG mode and enable automatic archiving:
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE ARCHIVELOG;
SQL> ALTER DATABASE OPEN;
3.2 Step-by-Step Instructions for Creating a Physical Standby Database
This section describes the tasks you perform to create a physical standby database.
Table 3-2 provides a checklist of the tasks that you perform to create a physical standby database and the database or databases on which you perform each task. There is also a reference to the section that describes the task in more detail. Table 3-2 Creating a Physical Standby Database
3.2.1 Create a Backup Copy of the Primary Database Datafiles
You can use any backup copy of the primary database to create the physical standby database, as long as you have the necessary archived redo log files to completely recover the database. Oracle recommends that you use the Recovery Manager utility (RMAN).
3.2.2 Create a Control File for the Standby Database
If the backup procedure required you to shut down the primary database, issue the following SQL*Plus statement to start the primary database:
SQL> STARTUP MOUNT;
Then, create the control file for the standby database, and open the primary database to user access, as shown in the following example:
SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE AS '/tmp/boston.ctl';
SQL> ALTER DATABASE OPEN;
Note:
You cannot use a single control file for both the primary and standby databases.
3.2.3 Prepare an Initialization Parameter File for the Standby Database
Perform the following steps to create a standby initialization parameter file.
Step 1 Copy the primary database parameter file to the standby database.
Create a text initialization parameter file (PFILE) from the server parameter file (SPFILE) used by the primary database; a text initialization parameter file can be copied to the standby location and modified. For example: SQL> CREATE PFILE='/tmp/initboston.ora' FROM SPFILE;
Later, in Section 3.2.5, you will convert this file back to a server parameter file after it is modified to contain the parameter values appropriate for use with the physical standby database. Step 2 Set initialization parameters on the physical standby database. Although most of the initialization parameter settings in the text initialization parameter file that you copied from the primary system are also appropriate for the physical standby database, some modifications need to be made. Example 3-5 shows the portion of the standby initialization parameter file where values were modified for the physical standby database. Parameter values that are different from Example 3-3 and Example 3-4 are shown in bold typeface. The parameters shown in Example 3-5 are valid for the Boston database when it is running in either the primary or the standby database role. Example 3-5 Modifying Initialization Parameters for a Physical Standby Database .
.
.
DB_NAME=chicago
DB_UNIQUE_NAME=boston
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston)'
CONTROL_FILES='/arch1/boston/control1.ctl', '/arch2/boston/control2.ctl'
DB_FILE_NAME_CONVERT='chicago','boston'
LOG_FILE_NAME_CONVERT=
'/arch1/chicago/','/arch1/boston/','/arch2/chicago/','/arch2/boston/'
LOG_ARCHIVE_FORMAT=log%t_%s_%r.arc
LOG_ARCHIVE_DEST_1=
'LOCATION=/arch1/boston/
VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
DB_UNIQUE_NAME=boston'
LOG_ARCHIVE_DEST_2=
'SERVICE=chicago LGWR ASYNC
VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)
DB_UNIQUE_NAME=chicago'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_STATE_2=ENABLE
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
STANDBY_FILE_MANAGEMENT=AUTO
FAL_SERVER=chicago
FAL_CLIENT=boston
.
.
.
Note that the example assumes the use of the LGWR process to transmit redo data to both the local and remote destinations on the LOG_ARCHIVE_DEST_2 initialization parameter.
In addition, ensure the COMPATIBLE initialization parameter is set to the same value on both the primary and standby databases. If the values differ, redo transport services may be unable to transmit redo data from the primary database to the standby databases. In a Data Guard configuration, COMPATIBLE must be set to a minimum of 9.2.0.1.0. However, if you want to take advantage of new Oracle Database 10g features, set the COMPATIBLE parameter to 10.2.0.0 or higher.
It is always a good practice to use the SHOW PARAMETERS command to verify no other parameters need to be changed.
The following table provides a brief explanation about the parameter settings shown in Example 3-5 that have different settings from the primary database.
Parameter | Recommended Setting |
| Specify a unique name for this database. This name stays with the database and does not change even if the primary and standby databases reverse roles. |
| Specify the path name for the control files on the standby database. Example 3-5 shows how to do this for two control files. It is recommended that a second copy of the control file is available so an instance can be easily restarted after copying the good control file to the location of the bad control file. |
| Specify the path name and filename location of the primary database datafiles followed by the standby location. This parameter converts the path names of the primary database datafiles to the standby datafile path names. If the standby database is on the same system as the primary database or if the directory structure where the datafiles are located on the standby site is different from the primary site, then this parameter is required. |
| Specify the location of the primary database online redo log files followed by the standby location. This parameter converts the path names of the primary database log files to the path names on the standby database. If the standby database is on the same system as the primary database or if the directory structure where the log files are located on the standby system is different from the primary system, then this parameter is required. |
| Specify where the redo data is to be archived. In Example 3-5: · LOG_ARCHIVE_DEST_1 archives redo data received from the primary database to archived redo log files in /arch1/boston/. · LOG_ARCHIVE_DEST_2 is currently ignored because this destination is valid only for the primary role. If a switchover occurs and this instance becomes the primary database, then it will transmit redo data to the remote Chicago destination. Note: If a flash recovery area was configured (with the DB_RECOVERY_FILE_DEST initialization parameter) and you have not explicitly configured a local archiving destination with the LOCATION attribute, Data Guard automatically uses the LOG_ARCHIVE_DEST_10 initialization parameter as the default destination for local archiving. See Section 5.2.3 for more information. Also, see Chapter 14 for complete information about LOG_ARCHIVE_DEST_n. |
| Specify the Oracle Net service name of the FAL server (typically this is the database running in the primary role). When the Boston database is running in the standby role, it uses the Chicago database as the FAL server from which to fetch (request) missing archived redo log files if Chicago is unable to automatically send the missing log files. See Section 5.8. |
| Specify the Oracle Net service name of the Boston database. The FAL server (Chicago) copies missing archived redo log files to the Boston standby database. See Section 5.8. |
Caution:
Review the initialization parameter file for additional parameters that may need to be modified. For example, you may need to modify the dump destination parameters (BACKGROUND_DUMP_DEST, CORE_DUMP_DEST, USER_DUMP_DEST) if the directory location on the standby database is different from those specified on the primary database. In addition, you may have to create directories on the standby system if they do not already exist. 3.2.4 Copy Files from the Primary System to the Standby System
Use an operating system copy utility to copy the following binary files from the primary system to the standby system:
3.2.5 Set Up the Environment to Support the Standby Database
Perform the following steps to create a Windows-based service, create a password file, set up the Oracle Net environment, and create a SPFILE.
Step 1 Create a Windows-based service.
If the standby system is running on a Windows-based system, use the ORADIM utility to create a Windows Service and password file. For example:
WINNT> oradim -NEW -SID boston -INTPWD password -STARTMODE manual
Step 2 Create a password file. On platforms other than Windows, create a password file, and set the password for the SYS user to the same password used by the SYS user on the primary database. The password for the SYS user on every database in a Data Guard configuration must be identical for redo transmission to succeed. See Oracle Database Administrator's Guide. Step 3 Configure listeners for the primary and standby databases. On both the primary and standby sites, use Oracle Net Manager to configure a listener for the respective databases. To restart the listeners (to pick up the new definitions), enter the following LSNRCTL utility commands on both the primary and standby systems:
% lsnrctl stop
% lsnrctl start
Step 4 Create Oracle Net service names. On both the primary and standby systems, use Oracle Net Manager to create a network service name for the primary and standby databases that will be used by redo transport services.
The Oracle Net service name must resolve to a connect descriptor that uses the same protocol, host address, port, and service that you specified when you configured the listeners for the primary and standby databases. The connect descriptor must also specify that a dedicated server be used.
Step 5 Create a server parameter file for the standby database. On an idle standby database, use the SQL CREATE statement to create a server parameter file for the standby database from the text initialization parameter file that was edited in Step 2. For example: SQL> CREATE SPFILE FROM PFILE='initboston.ora';
3.2.6 Start the Physical Standby Database
Perform the following steps to start the physical standby database and Redo Apply.
Step 1 Start the physical standby database.
On the standby database, issue the following SQL statement to start and mount the database:
SQL> STARTUP MOUNT;
On the standby database, issue the following command to start Redo Apply: SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;
Step 3 Test archival operations to the physical standby database. In this example, the transmission of redo data to the remote standby location does not occur until after a log switch. A log switch occurs, by default, when an online redo log file becomes full. To force a log switch so that redo data is transmitted immediately, use the following ALTER SYSTEM statement on the primary database. For example: SQL> ALTER SYSTEM SWITCH LOGFILE;
3.2.7 Verify the Physical Standby Database Is Performing Properly
Once you create the physical standby database and set up redo transport services, you may want to verify database modifications are being successfully transmitted from the primary database to the standby database.
To see that redo data is being received on the standby database, you should first identify the existing archived redo log files on the standby database, force a log switch and archive a few online redo log files on the primary database, and then check the standby database again. The following steps show how to perform these tasks.
Step 1 Identify the existing archived redo log files.
On the standby database, query the V$ARCHIVED_LOG view to identify existing files in the archived redo log. For example:
SQL> SELECT SEQUENCE#, FIRST_TIME, NEXT_TIME
2 FROM V$ARCHIVED_LOG ORDER BY SEQUENCE#;
SEQUENCE# FIRST_TIME NEXT_TIME
---------- ------------------ ------------------
8 11-JUL-02 17:50:45 11-JUL-02 17:50:53
9 11-JUL-02 17:50:53 11-JUL-02 17:50:58
10 11-JUL-02 17:50:58 11-JUL-02 17:51:03
3 rows selected.
Step 2 Force a log switch to archive the current online redo log file. On the primary database, issue the ALTER SYSTEM SWITCH LOGFILE statement to force a log switch and archive the current online redo log file group:
SQL> ALTER SYSTEM SWITCH LOGFILE;
Step 3 Verify the new redo data was archived on the standby database. On the standby database, query the V$ARCHIVED_LOG view to verify the redo data was received and archived on the standby database:
SQL> SELECT SEQUENCE#, FIRST_TIME, NEXT_TIME
2> FROM V$ARCHIVED_LOG ORDER BY SEQUENCE#;
SEQUENCE# FIRST_TIME NEXT_TIME
---------- ------------------ ------------------
8 11-JUL-02 17:50:45 11-JUL-02 17:50:53
9 11-JUL-02 17:50:53 11-JUL-02 17:50:58
10 11-JUL-02 17:50:58 11-JUL-02 17:51:03
11 11-JUL-02 17:51:03 11-JUL-02 18:34:11
4 rows selected.
The archived redo log files are now available to be applied to the physical standby database.
Step 4 Verify new archived redo log files were applied. On the standby database, query the V$ARCHIVED_LOG view to verify the archived redo log files were applied.
SQL> SELECT SEQUENCE#,APPLIED FROM V$ARCHIVED_LOG
2 ORDER BY SEQUENCE#;
SEQUENCE# APP
--------- ---
8 YES
9 YES
10 YES
11 YES
4 rows selected.
3.3 Post-Creation Steps
At this point, the physical standby database is running and can provide the maximum performance level of data protection. The following list describes additional preparations you can take on the physical standby database:
· Upgrade the data protection mode
The Data Guard configuration is initially set up in the maximum performance mode (the default). See Section 5.6 for information about the data protection modes and how to upgrade or downgrade the current protection mode. · Enable Flashback Database
Flashback Database removes the need to re-create the primary database after a failover. Flashback Database enables you to return a database to its state at a time in the recent past much faster than traditional point-in-time recovery, because it does not require restoring datafiles from backup nor the extensive application of redo data. You can enable Flashback Database on the primary database, the standby database, or both. See Section 12.4 and Section 12.5 for scenarios showing how to use Flashback Database in a Data Guard environment. Also, see Oracle Database Backup and Recovery Advanced User's Guide for more information about Flashback Database.
