Segment large backup objects

To assist backing up and restoring of database objects that are larger than 1 TB, use the IBM Spectrum Protect™ for Enterprise Resource Planning SEGMENTSIZE keyword parameter for each DB2® backup session to be partitioned into multiple segments. These segments are stored on IBM Spectrum Protect as individual backup objects. The value of the SEGMENTSIZE keyword parameter determines the maximum allowable size of a backup segment on IBM Spectrum Protect storage.

Each DB2 backup session is assigned its own backup segment group. A backup segment group is a collection of all segments of a backup session that is generated by IBM Spectrum Protect for ERP during a database backup operation. For example, two DB2 backup sessions (s1, s2) that contain two segments for each session (seg1, seg2), is assigned two backup segment groups (sg1, sg2). The first backup segment group (sg1) contains segments s1:seg1, s1:seg2. The second backup segment group (sg2) contains segments s2:seg1, s2:seg2.

When you specify segmentation, the session number substring of the backup image name is used to identify the backup object as part of a segmented data stream. The session number substring segment number is added to the backup image name that is separated by a colon (:). For example:

DB2 instance.db alias.type.partition number.DB2 backup ID.session number:segment number

When IBM Spectrum Protect for ERP initiates a change of IBM Spectrum Protect objects, the segment number, for the new backup object segment, increases by one.

For integrity check processing of the backup segment group, an extra zero-byte backup object, the so-called commit object, is generated. This object is used by IBM Spectrum Protect for ERP to check the integrity of the related backup segment group. The naming convention of the commit object is as follows:

DB2 instance.db alias.type.partition number.DB2 backup ID.session number:C last segment number

The character C following the colon (:) character identifies the backup image as a committed object. These committed objects are stored on IBM Spectrum Protect at the very end of each participating backup session. Also, the last segment number identifies the number of segments that must exist on IBM Spectrum Protect for all segments for that session to be restored. As a result, this update to the backup image name ensures that the correct object is assigned to the correct DB2 backup session. However, when one or more committed objects are missing, the integrity of the backup segment group is not guaranteed. For this reason, the database restore is not started by IBM Spectrum Protect for ERP

You can verify whether backup object segmentation was activated by using either of these methods:

IBM Spectrum Protect for ERP log entries: An information message that identifies that the maximum segment size is logged to this file. The session number substring :segment number is included in the backup image name, and in an information message that indicates that a commit object (containing substring Clast segment number) was generated.
DB2 Backup Object Manager: The session number substring :segment number is visible in the backup image that is displayed by the q_all -m detailed, q_db -m detailed or q_raw command.

Segmentation and IBM Spectrum Protect server

If segmentation is used for backup operations, the IBM Spectrum Protect server might issue the error message,"ANS0326E This node exceeds its maximum number of mount points. This situation happens because there might be a short delay before IBM Spectrum Protect actually closes client sessions. To overcome this problem, the IBM Spectrum Protect server MAXNUMMP parameter for the IBM Spectrum Protect node is set to twice the number of IBM Spectrum Protect sessions that are used for the backup.

The number of active parallel sessions for IBM Spectrum Protect for ERP to the IBM Spectrum Protect server is limited by the IBM Spectrum Protect for ERP parameters SESSION, in the SERVER stanza, and MAX_SESSIONS.

For example, if two IBM Spectrum Protect sessions are needed for the database backup, the MAXNUMMP parameter for the used node is set to four in the IBM Spectrum Protect server. In this example, IBM Spectrum Protect for ERP sends the data by using two IBM Spectrum Protect sessions only.

Segmentation and backup processing

Review the following backup characteristics before you apply segmentation to your DB2 backup operations:

The data stream that is sent from DB2 is segmented during a DB2 database backup.
When implemented, segmentation is applied to every participating DB2 backup session.
Back up and restore sessions are isolated from each other. As a result, segments that are generated by IBM Spectrum Protect for ERP are isolated on a per session basis. Therefore, segments cannot be mixed between different sessions. All segments that are backed up within the same session are restored in the same session.
DB2 logs are not partitioned in to multiple segments.

Segmentation and restore processing

Review the following restore characteristics before you apply segmentation to your DB2 restore operations:

Metadata that is associated with the backup object indicates whether the object is part of a segmented data stream. If the backup object is part of a segmented data stream, IBM Spectrum Protect for ERP automatically joins the segments to the object DB2 expects to receive from IBM Spectrum Protect during the restore operation.
Back up and restore sessions are isolated from each other. As a result, segments that are generated by IBM Spectrum Protect for ERP are isolated on a per session basis. Therefore, segments cannot be mixed between different sessions. All segments that are backed up within the same session are restored in the same session.
Do not use segmentation into two or more segments for a backup that is to be restored to DB2 by using the Backup Object Manager command backom -c r_raw .... This backup can be restored to the destination directory, but not into DB2 if two or more segments were created. If the backup was created by using a single segment, it can be restored to DB2 from the destination directory after retrieval from IBM Spectrum Protect. There is no limitation that concerns segmentation for other restore methods.