Online Backup Strategies and Limitations on Directory Server v6.x versions

Answer

Online backup is supported for Directory Server v6.x versions.

There are three approaches:

• First, one can use the idsdb2ldif utility. This approach is slow for large directories, but for directories of fewer than 200,000 entries, it is sufficient.

• The second approach is to use DB2 online backup, which is supported for TDS v6.x and later releases .

• The third approach is to use RAID mirroring facilities for online backup.

DB2 online backup is supported for v6.0, just as it is for v6.1 and later releases. To use this feature, you must set the logretain configuration parameter for the database to 'recovery'.

However, there is one circumstance in which online backup can't be used.
1. If Directory Server is configured to use SMS tablespaces AND those tablespaces contain large object (LOB) data AND the directory is handling write activity (either directly or replicated) then DB2 online backup must not be used, and can cause the directory to hang. SMS tablespaces are the default V6.0 and V6.1 configuration
2. DB2 online backup can always be used if the directory is using DMS or DMS Large tablespaces or Auto Storage enabled tablespaces.

Additional considerations for V6.0 and V6.1 default configurations:
If SMS tablespaces are used, it is necessary to check for LOB data. You can use the following commands, when logged on as the database administrator, to check for LOB data:

db2 connect to <database>
db2 update monitor switches using table on
(wait 5 minutes)
db2 get snapshot for tables on <database> >snap.out
db2 connect reset

The snap.out file may contain lines for certain tables labled "LOB Object pages". If no such lines are found, or if the number of LOB Object pages is 1 in each case where the line exists, then no LOB data is present. If the the directory uses SMS tablespaces and has LOB data, one can still do online DB2 backup, providing that no writes, including replicated writes, occur during the backup interval. If a TDS server is used as a replica, or if it is a standby peer master, you can disable writes to it by suspending replication from the active master to the peer or replica, and then you can proceed with backup. Replication should be resumed as soon as the backup has completed.

Note: Backing up TDS using DB2 utilities requires that the <ITDS instance home>/etc (ex: /home/ldapdb2/idsslapd-ldapdb2/etc) directory be backed up separately. The configuration information contained in this directory is important in recovering the TDS instance from a backup. The idsdbback utility that does offline backup does this automatically.

Use of RAID mirroring for DB2 online backup is described at the following link: http://www.ibm.com/developerworks/db2/library/techarticle/0204quazi/0204quazi.html

Related Information and Technotes

ITDS Log Management for Online Backups

Performance Tuning for ITDS Redbook