DB2 High Availability disaster recovery (HADR) Restrictions

Environment product: DB2 UDB

Platform: cross-platform

Version: 8.2 (8.1 patch 7)

Problem DB2 UDB High Availability disaster recovery (HADR) is a database replication feature that provides high availability solutions for partial and entire site faults. HADR copies data changes from the source database (called the master database) to the target database (called the backup database) to prevent data loss. This data replication operation is implemented through the database log. Here we will introduce the restrictions on HADR When configuring and using HADR.

A summary of the restrictions on High Availability disaster recovery (HADR) is as follows:

1. HADR is only supported on DB2 UDB Enterprise Server version (ESE. However, HADR is not supported when ESE has multiple database partitions.

2. The master database and the slave database must have the same operating system version and the same DB2 UDB version, except for a short period of time during the alternate rolling upgrade process.

3. the DB2 UDB release on the primary and standby databases must have the same bit size (32-bit or 64-bit ).

4. Read operations on the standby database are not supported. The client cannot connect to the standby database.

5. Logs can only be archived by the current primary database.

6. Backup operations are not supported on the backup database.

7. Non-(log) record operations cannot be copied to the standby database.

Because HADR uses database logs to copy data to the standby database, non-record operations are allowed in the primary database, but such operations are not allowed to be copied to the standby database. These non-copy operations include (but are not limited to) the following ):

1) Use the specified not logged initially option to create a table.

2) BLOB and CLOB fields. Although these fields are not copied, they are allocated space in the standby database.

3) use the update database configuration and update database manager configuration commands to UPDATE the database configuration.

4) restore the history file and change the history file.

8. The Mount operation with the specified copy no option is not supported.

9. DataLink is not supported.

10. raw logs are not supported.

HADR does not support using raw I/O (direct disk access) for database log files ). If you use the start hadr command to start hadr, or if you restart the database After configuring HADR, the original log is detected, the error that causes the associated command to fail and causes SQL1768N cause code "9", namely:

Configure the database to use raw logs. However, HADR does not support using raw I/O (direct disk access) for database log files ).

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