| Oracle® Data Guard Concepts and Administration 11g Release 2 (11.2) Part Number E10700-01 |
|
|
View PDF |
| Oracle® Data Guard Concepts and Administration 11g Release 2 (11.2) Part Number E10700-01 |
|
|
View PDF |
Starting with Oracle Database 10g release 1 (10.1.0.3), you can use a logical standby database to perform a rolling upgrade of Oracle Database 10g software. During a rolling upgrade, you can run different releases of an Oracle database on the primary and logical standby databases while you upgrade them, one at a time, incurring minimal downtime on the primary database.
Note:
This chapter describes an alternative to the usual upgrade procedure involving longer downtime, as described in Appendix B, "Upgrading Databases in a Data Guard Configuration". Do not attempt to combine steps from the method described in this chapter with steps from Appendix B.The instructions in this chapter describe how to minimize downtime while upgrading an Oracle database. This chapter provides the following topics:
Performing a Rolling Upgrade By Creating a New Logical Standby Database
Performing a Rolling Upgrade With an Existing Logical Standby Database
Performing a Rolling Upgrade With an Existing Physical Standby Database
Performing a rolling upgrade with SQL Apply provides several advantages:
Your database will incur very little downtime. The overall downtime can be as little as the time it takes to perform a switchover.
You eliminate application downtime due to PL/SQL recompilation.
You can validate the upgraded database release without affecting the primary database.
The rolling upgrade procedure requires the following:
A primary database that is running Oracle Database release x and a logical standby database that is running Oracle Database release y.
The databases must not be part of a Data Guard Broker configuration. See Oracle Data Guard Broker for information about removing databases from a broker configuration.
The Data Guard protection mode must be set to either maximum availability or maximum performance. Query the PROTECTION_LEVEL column in the V$DATABASE view to find out the current protection mode setting.
To ensure the primary database can proceed while the logical standby database is being upgraded, the LOG_ARCHIVE_DEST_n initialization parameter for the logical standby database destination must not be set to MANDATORY.
The COMPATIBLE initialization parameter must match the software release prior to the upgrade. That is, a rolling upgrade from release x to release y requires that the COMPATIBLE initialization parameter be set to release x on both the primary and standby databases.
Figure 12-1 shows a Data Guard configuration before the upgrade begins, with the primary and logical standby databases both running the same Oracle Database software release.
Figure 12-1 Data Guard Configuration Before Upgrade
During the upgrade process, the Data Guard configuration operates with mixed database releases at several points in this process. Data protection is not available across releases. During these steps, consider having a second standby database in the Data Guard configuration to provide data protection.
The steps and figures describing the upgrade procedure refer to the databases as Database A and Database B rather than as the primary database and standby database. This is because the databases switch roles during the upgrade procedure. Initially, Database A is the primary database and Database B is the logical standby database, as shown in Figure 12-1.
The following sections describe scenarios in which you can use the SQL Apply rolling upgrade procedure:
This scenario assumes that you do not have an existing Data Guard configuration, but you are going to create a logical standby database solely for the purpose of performing a rolling upgrade of the Oracle Database.
Table 12-1 lists the steps to prepare the primary and standby databases for upgrading.
To identify unsupported database objects on the primary database and decide how to handle them, follow these steps:
Identify unsupported data types and storage attributes for tables:
Review the list of supported data types and storage attributes provided in Appendix C, "Data Type and DDL Support on a Logical Standby Database".
Query the DBA_LOGSTDBY_UNSUPPORTED and DBA_LOGSTDBY_SKIP views on the primary database. Changes that are made to the listed tables and schemas on the primary database will not be applied on the logical standby database. Use the following query to see a list of unsupported tables:
SQL> SELECT DISTINCT OWNER, TABLE_NAME FROM DBA_LOGSTDBY_UNSUPPORTED;
Use the following query to see a list of unsupported internal schemas:
SQL> SELECT OWNER FROM DBA_LOGSTDBY_SKIP - > WHERE STATEMENT_OPT = 'INTERNAL SCHEMA';
Decide how to handle unsupported tables.
If unsupported objects are being modified on your primary database, it might be possible to perform the upgrade anyway by temporarily suspending changes to the unsupported tables for the period of time it takes to perform the upgrade procedure.
If you can prevent changes to unsupported data, then using SQL Apply might still be a viable way to perform the upgrade procedure. This method requires that you prevent users from modifying any unsupported tables from the time you create the logical standby control file to the time you complete the upgrade. For example, assume that the Payroll department updates an object table, but that department updates the database only Monday through Friday. However, the Customer Service department requires database access 24 hours a day, 7 days a week, but uses only supported data types and tables. In this scenario, you could perform the upgrade over a weekend. You can monitor transaction activity in the DBA_LOGSTDBY_EVENTS view and discontinue the upgrade (if necessary) up to the time you perform the first switchover.
If you cannot prevent changes to unsupported tables during the upgrade, any unsupported transactions that occur are recorded in the DBA_LOGSTDBY_EVENTS table on the logical standby database. After the upgrade is completed, you might be able to use the Oracle Data Pump Export/Import utility to import the changed tables to the upgraded databases.
The size of the changed tables will determine how long database operations will be unavailable, so you must decide if a table is too large to export and import its data into the standby database. For example, a 4-terabyte table is not a good candidate for the export/import process.
Note:
If you cannot use a logical standby database because the data types in your application are unsupported, then perform the upgrade as documented in Oracle Database Upgrade Guide.To create a logical standby database, follow the instructions in Chapter 4.
Note:
Before you start SQL Apply for the first time, make sure you capture information about transactions running on the primary database that will not be supported by a logical standby database. Run the following procedures to capture and record the information as events in the
DBA_LOGSTDBY_EVENTS table:
EXECUTE DBMS_LOGSTDBY.APPLY_SET('MAX_EVENTS_RECORDED',
DBMS_LOGSTDBY.MAX_EVENTS);
EXECUTE DBMS_LOGSTDBY.APPLY_SET('RECORD_UNSUPPORTED_OPERATIONS',
'TRUE');
See Also:
Section 10.5.1, "Customizing Logging of Events in the DBA_LOGSTDBY_EVENTS View" for more information about the DBA_LOGSTDBY_EVENTS view
Oracle Database PL/SQL Packages and Types Reference for complete information about the DBMS_LOGSTDBY package
Oracle recommends configuring a standby redo log on the logical standby database to minimize downtime.
Now that you have created a logical standby database, you can follow the procedure described in Section 12.5, "Performing a Rolling Upgrade With an Existing Logical Standby Database", which assumes that you have a logical standby running the same Oracle software.
This section provides a step-by-step procedure for upgrading the logical standby database and the primary database. Table 12-2 lists the steps.
Follow these steps to prepare to perform a rolling upgrade of Oracle Software:
Stop SQL Apply by issuing the following statement on the logical standby database (Database B):
SQL> ALTER DATABASE STOP LOGICAL STANDBY APPLY;
Set compatibility, if needed, to the highest value.
Ensure the COMPATIBLE initialization parameter specifies the release number for the Oracle Database software running on the primary database prior to the upgrade.
For example, if the primary database is running release 10.1, then set the COMPATIBLE initialization parameter to 10.1 on both databases. Be sure to set the COMPATIBLE initialization parameter on the standby database first before you set it on the primary database.
Upgrade Oracle database software on the logical standby database (Database B) to release y. While the logical standby database is being upgraded, it will not accept redo data from the primary database.
To upgrade Oracle Database software, refer to the Oracle Database Upgrade Guide for the applicable Oracle Database release.
Figure 12-2 shows Database A running release x, and Database B running release y. During the upgrade, redo data accumulates on the primary system.
Figure 12-2 Upgrade the Logical Standby Database Release
Restart SQL Apply and operate with release x on Database A and release y on Database B. To start SQL Apply, issue the following statement on Database B:
SQL> ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE;
The redo data that was accumulating on the primary system is automatically transmitted and applied on the newly upgraded logical standby database. The Data Guard configuration can run the mixed releases shown in Figure 12-3 for an arbitrary period while you verify that the upgraded Oracle Database software release is running properly in the production environment.
To monitor how quickly Database B is catching up to Database A, query the V$LOGSTDBY_PROGRESS view on Database B. For example:
SQL> ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YY HH24:MI:SS'; Session altered. SQL> SELECT SYSDATE, APPLIED_TIME FROM V$LOGSTDBY_PROGRESS; SYSDATE APPLIED_TIME ------------------ ------------------ 27-JUN-05 17:07:06 27-JUN-05 17:06:50
You should frequently query the DBA_LOGSTDBY_EVENTS view to learn if there are any DDL and DML statements that have not been applied on Database B. Example 12-1 demonstrates how monitoring events can alert you to potential differences in the two databases.
Example 12-1 Monitoring Events with DBA_LOGSTDBY_EVENTS
SQL> SET LONG 1000 SQL> SET PAGESIZE 180 SQL> SET LINESIZE 79 SQL> SELECT EVENT_TIMESTAMP, EVENT, STATUS FROM DBA_LOGSTDBY_EVENTS - > ORDER BY EVENT_TIMESTAMP; EVENT_TIMESTAMP --------------------------------------------------------------------------- EVENT -------------------------------------------------------------------------------- STATUS -------------------------------------------------------------------------------- … 24-MAY-05 05.18.29.318912 PM CREATE TABLE SYSTEM.TST (one number) ORA-16226: DDL skipped due to lack of support 24-MAY-05 05.18.29.379990 PM "SYSTEM"."TST" ORA-16129: unsupported dml encountered
In the preceding example:
The ORA-16226 error shows a DDL statement that could not be supported. In this case, it could not be supported because it belongs to an internal schema.
The ORA-16129 error shows that a DML statement was not applied.
These types of errors indicate that not all of the changes that occurred on Database A have been applied to Database B. At this point, you must decide whether or not to continue with the upgrade procedure. If you are certain that this difference between the logical standby database and the primary database is acceptable, then continue with the upgrade procedure. If not, discontinue and reinstantiate Database B and perform the upgrade procedure at another time.
When you are satisfied that the upgraded database software is operating properly, perform a switchover to reverse the database roles by issuing the following statement on Database A:
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO LOGICAL STANDBY;
This statement must wait for existing transactions to complete. To minimize the time it takes to complete the switchover, users still connected to Database A should log off immediately and reconnect to Database B.
Note:
The usual two-phased prepared switchover described in Section 8.3.1 cannot be used because it requires both primary and standby databases to be running the same version of the Oracle software and at this point, the primary database is running a lower version of the Oracle software. Instead, the single-phased unprepared switchover procedure documented above is used. The unprepared switchover should only be used in the context of a rolling upgrade using a logical standby database.Note:
If you suspended activity to unsupported tables or packages on Database A when it was the primary database, you must continue to suspend the same activities on Database B while it is the primary database if you eventually plan to switch back to Database A.Step 4 "Monitor events on the upgraded standby database" described how to list unsupported tables that are being modified. If unsupported DML statements were issued on the primary database (as described in Example 12-1), import the latest version of those tables using an import utility such as Oracle Data Pump.
For example, the following import command truncates the scott.emp table and populates it with data matching the former primary database (A):
IMPDP SYSTEM NETWORK_LINK=DATABASEA TABLES=SCOTT.EMP TABLE_EXIST_ACTION=TRUNCATE
Note that this command will prompt you for the impdp password before executing.
When you are satisfied that the upgraded database software is operating properly, complete the switchover to reverse the database roles:
On Database B, query the SWITCHOVER_STATUS column of the V$DATABASE view, as follows:
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE; SWITCHOVER_STATUS -------------------- TO PRIMARY
When the SWITCHOVER_STATUS column displays TO PRIMARY, complete the switchover by issuing the following statement on Database B:
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
Note:
The usual two-phased prepared switchover described in Section 8.3.1 cannot be used because it requires both primary and standby databases to be running the same version of the Oracle software and at this point, the primary database is running a lower version of the Oracle software. Instead, the single-phased unprepared switchover procedure documented above is used. The unprepared switchover should only be used in the context of a rolling upgrade using a logical standby database.Activate the user applications and services on Database B, which is now running in the primary database role.
After the switchover, you cannot send redo data from the new primary database (B) that is running the new database software release to the new standby database (A) that is running an older software release. This means the following:
Redo data is accumulating on the new primary database.
The new primary database is unprotected at this time.
Figure 12-4 shows Database B, the former standby database (running release y), is now the primary database, and Database A, the former primary database (running release x), is now the standby database. The users are connected to Database B.
If Database B can adequately serve as the primary database and your business does not require a logical standby database to support the primary database, then you have completed the rolling upgrade process. Allow users to log in to Database B and begin working there, and discard Database A when it is convenient. Otherwise, continue with step 8.
Database A is still running release x and cannot apply redo data from Database B until you upgrade it and start SQL Apply.
For more information about upgrading Oracle Database software, see the Oracle Database Upgrade Guide for the applicable Oracle Database release.
Figure 12-5 shows the system after both databases have been upgraded.
Issue the following statement to start SQL Apply on Database A and, if necessary, create a database link to Database B:
SQL> ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE NEW PRIMARY db_link_to_b;
Note:
You will need to create a database link (if one has not already been set up) and to use theNEW PRIMARY clause, because in Step 4 the single-phased unprepared switchover was used to turn Database A into a standby database.
You will need to connect as SYS user or with an account with similar level of privileges for the database link.
When you start SQL Apply on Database A, the redo data that is accumulating on the primary database (B) is sent to the logical standby database (A). The primary database is protected against data loss once all the redo data is available on the standby database.
Raise the compatibility level of both databases by setting the COMPATIBLE initialization parameter. You must raise the compatibility level at the logical standby database before you raise it at the primary database. Set the COMPATIBLE parameter on the standby database before you set it on the primary database. See Oracle Database Reference for more information about the COMPATIBLE initialization parameter.
To ensure that all changes performed on Database B are properly applied to the logical standby database (A), you should frequently query the DBA_LOGSTDBY_EVENTS view, as you did for Database A in step 4. (See Example 12-1.)
If changes were made that invalidate Database A as a copy of your existing primary database, you can discard Database A and create a new logical standby database in its place. See Chapter 4, "Creating a Logical Standby Database" for complete information.
Optionally, perform another switchover of the databases so Database A is once again running in the primary database role (as shown in Figure 12-1).
Note:
You will use the two-phased prepared switchover described in Section 8.3.1 since at this time, both Database A and Database B are running the same version of the Oracle software.The steps in this section show you how to perform a rolling upgrade of Oracle software and then get back to your original configuration in which A is the primary database and B is the physical standby database, and both of them are running the upgraded Oracle software.
Note:
The steps in this section assume that you have a primary database (A) and a physical standby database (B) already set up and using Oracle Database release 11.1 or later.Table 12-3 summarizes the steps involved.
Table 12-3 Steps to Perform a Rolling Upgrade With an Existing Physical Standby
Enable Flashback Database, if it is not already enabled:
SQL> SHUTDOWN IMMEDIATE; SQL> STARTUP MOUNT; SQL> ALTER DATABASE FLASHBACK ON; SQL> ALTER DATABASE OPEN;
Create a guaranteed restore point:
SQL> CREATE RESTORE POINT pre_upgrade GUARANTEE FLASHBACK DATABASE;
Follow the steps outlined in Chapter 4, "Creating a Logical Standby Database" except for the following difference. In Section 4.2.4.1, "Convert to a Logical Standby Database" you must use a different command to convert the logical standby database. Instead of ALTER DATABASE RECOVER TO LOGICAL STANDBY db_name, issue the following command:
SQL> ALTER DATABASE RECOVER TO LOGICAL STANDBY KEEP IDENTITY; SQL> ALTER DATABASE OPEN;
You must take the following actions before you start SQL Apply for the first time:
Disable automatic deletion of foreign archived logs at the logical standby, as follows:
SQL> EXECUTE DBMS_LOGSTDBY.APPLY_SET('LOG_AUTO_DELETE', 'FALSE');
Note:
You should not delete any remote archived logs processed by the logical standby database (Database B). These remote archived logs are required later during the rolling upgrade process. If you are using the recovery area to store the remote archived logs, you must ensure that it has enough space to accommodate these logs without interfering with the normal operation of the logical standby database.Make sure you capture information about transactions running on the primary database that will not be supported by a logical standby database. Run the following procedures to capture and record the information as events in the DBA_LOGSTDBY_EVENTS table:
SQL> EXECUTE DBMS_LOGSTDBY.APPLY_SET('MAX_EVENTS_RECORDED', -
> DBMS_LOGSTDBY.MAX_EVENTS);
SQL> EXECUTE DBMS_LOGSTDBY.APPLY_SET('RECORD_UNSUPPORTED_OPERATIONS', 'TRUE');
Start SQL Apply for the first time, as follows:
SQL> ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE;
See Also:
Section 10.5.1, "Customizing Logging of Events in the DBA_LOGSTDBY_EVENTS View" for more information about the DBA_LOGSTDBY_EVENTS view
Oracle Database PL/SQL Packages and Types Reference for complete information about the DBMS_LOGSTDBY package
You can now follow Steps 1 through 8 as described in Section 12.5, "Performing a Rolling Upgrade With an Existing Logical Standby Database". At the end of these steps, Database B will be your primary database running the upgraded version of the Oracle software, and Database A has become your logical standby database.
Move on to the next step to turn Database A into the physical standby for Database B.
SQL> SHUTDOWN IMMEDIATE; SQL> STARTUP MOUNT; SQL> FLASHBACK DATABASE TO RESTORE POINT pre_upgrade; SQL> SHUTDOWN IMMEDIATE;
At this point, you should switch the Oracle binary at Database A to use the higher version of the Oracle software. You will not run the upgrade scripts, since Database A will be turned into a physical standby, and will be upgraded automatically as it applies the redo data generated by Database B.
Mount Database A, as follows:
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY; SQL> SHUTDOWN IMMEDIATE;
Database A will be upgraded automatically as it applies the redo data generated by Database B. Managed recovery will wait until the new incarnation branch from the primary is registered before it starts applying redo.
SQL> STARTUP MOUNT; SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE - > DISCONNECT FROM SESSION;
Note:
When Redo Apply restarts, it waits for a new incarnation from the current primary database (Database B) to be registered.At this point, Database B is your primary database and Database A is your physical standby, both running the higher version of the Oracle software. To make Database A the primary database, follow the steps described in Section 8.2.1, "Performing a Switchover to a Physical Standby Database".
To preserve disk space, drop the existing guaranteed restore point:
SQL> DROP RESTORE POINT PRE_UPGRADE;
See Also:
The "Database Rolling Upgrade Using Transient Logical Standby: Oracle Data Guard 11g" best practices white paper available on the Oracle Maximum Availability Architecture (MAA) home page at:
|
 Copyright © 1999, 2009, Oracle and/or its affiliates. All rights reserved. Legal Notices |
|