SQL Replication

Compatibility between SQL Replication Version 10.1 on Linux, UNIX, and Windows and earlier versions

The change from 10-byte to 16-byte log sequence numbers (LSN) in DB2® 10.1 for Linux, UNIX, and Windows requires that you plan for compatibility of mixed-level or mixed-platform Capture servers, Apply servers, and Apply control servers.

To work with DB2 10.1, all replication control tables that store an LSN value and the programs that read and update the control tables must be updated. The new data type that is used to store LSNs in the control tables is VARCHAR(16) FOR BIT DATA.

Replication uses two methods to determine whether to use 16-byte LSN values or the older 10-byte LSNs: the COMPATIBILITY column in the IBMSNAP_CAPPARMS table and the ARCH_LEVEL column in the IBMSNAP_SUBS_SET table:

If Capture is at Version 10.1 and the value of COMPATIBILITY is 1001, Capture uses 16-byte LSNs. The Apply program must be at Version 10.1 to handle the longer LSNs, and the value of ARCH_LEVEL in the IBMSNAP_SUB_SET table must be 1001.
The Capture and Apply program use 10-byte LSNs under these conditions:
- Capture is at Version 9.7. A Version 10.1 Apply program can handle 10-byte log sequence numbers from an older Capture program.
- Capture is at Version 10.1 and the value of COMPATIBILITY is 0801. Apply can be pre-Version 10.1 or at Version 10.1. You must set ARCH_LEVEL in the IBMSNAP_SUB_SET table to 0801. This configuration is only supported for unidirectional replication and if the value of the COMMIT_COUNT column in the ASN.IBMSNAP_SUBS_SET table is null.

Table 1 summarizes the compatibility support.

Table 1. Supported Apply versions and compatibility settings for Version 10.1 Capture program. "Pre-V10.1" refers to Version 9.7 or earlier on Linux, UNIX, and Windows or Version 10.1 or earlier on z/OS.
Capture version	Capture compatibility setting	Capture LSN data length	Apply version	Apply LSN data length	IBMSNAP_SUB_SET.ARCH_LEVEL setting
Pre-V10.1	NA	10 bytes	Any	10	0801
V10.1	0801	10 bytes	Any ¹	10	0801
	1001	16 bytes	V10	16	1001
	1001	16 bytes	V9.7 or below	Not allowed
V10.1 with two or more DB2 pureScale® members	Capture compatibility setting of 0801 and data length of 10 are not allowed
	1001	16 bytes	V9.7 or below	Not allowed
			V10	Data length of 10 and ARCH_LEVEL of 0801 are not allowed
			V10	16	1001

A pre-Version 10.1 Apply program can only work with the V10.1 Capture program in unidirectional configurations and if the value of the COMMIT_COUNT column in the ASN.IBMSNAP_SUBS_SET table is null.

Other compatibility considerations:

For DB2 10.1 with more than one pureScale member, the value of the COMPATIBILITY column must be 1001.
The replication programs always use 10-byte LSNs if either the source or target server is on z/OS®.
The replication administration tools only create control tables with an ARCH_LEVEL of 1001 on DB2 10.1 for Linux, UNIX, and Windows.

Note: In terms of compatibility, SQL Replication Version 10.5 on Linux, UNIX, and Windows is equivalent to SQL Replication Version 10.1 on Linux, UNIX, and Windows.

Apply program support

A Version 10.1 Apply program supports both Version 9 and Version 10.1 Apply control servers. The Apply program queries the ARCH_LEVEL column in the IBMSNAP_APPLEVEL table to determine the level of the Apply control tables.

The V10.1 Apply program also queries the COMPATIBILITY column of the IBMSNAP_CAPPARMS table to determine whether the Capture program is using 16-byte LSNs. If the COMPATIBILITY column does not exist (pre-V10.1), Apply assumes 10-byte LSNs. The Apply program queries the ARCH_LEVEL column in the IBMSNAP_SUBS_SET table to determine the level of the subscription set and this must match the COMPATIBILITY value.

Important: Pre-V10.1 Apply programs cannot handle 16-byte LSNs. If this type of LSN is encountered, Apply does not stop processing the subscription set, meaning that data might be incorrect. If you migrate the Apply control tables to V10.1, do not use an Apply program that is at Version 9.7 or earlier.

Compatibility of CCD target tables

When you create CCD target tables, the replication administration tools rely on the Capture compatibility value to determine the length of the IBMSNAP_COMMITSEQ and IBMSNAP_INTENTSEQ columns in the CCD tables.

If the compatibility value is 1001, the tools create CCD target tables with 16-byte LSN columns. If the value is 0801, the tools create CCD targets with 10-byte LSNs.

When you create Q subscriptions with CCD tables as both source and target, the administration tools require that source and target CCD tables use the same data length for columns that store LSNs; that is, 16 byte to 16 byte, and 10 byte to 10 byte.

External CCD sources

External CCD source tables, which are not maintained by the Capture program, are supported by the V10.1 Apply program whether the tables have 10-byte or 16-byte LSN column lengths. Pre-V10.1 Apply progams only support external CCD tables that use 10-byte LSNs.

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Last updated: 2013-10-25