APAR PH02437 introduces the new DSNB233I message in Db2 12 and Db2 11. The new message reminds you to convert page sets to the extended 10-byte RBA or LRSN format, to avoid outages that might occur if Db2 reaches the 6-byte logging limit. Db2 (with APAR PH08298 applied) issues the DSNB233I message only for the first 20 pagesets opened that remain in the 6-byte format.
Db2 11 introduced support for the extended 10-byte RBA and LRSN, and you have the option to convert the bootstrap data set (BSDS) to the 10-byte format as soon as you migrate to Db2 11 new-function mode. Also, the BSDS conversion is mandatory before you can start migration to Db2 12, and it must be completed in Db2 11 new-function mode.
You can convert the BSDS without converting the page sets for Db2 catalog, directory and user objects right away. However, converting the BSDS and not converting the pagesets has some important catches, especially for non-data-sharing Db2 subsystems:
- After the BSDS conversion, Db2 stops issuing messages such as DSNJ032I or DSNJ034I, which warn you when that Db2 is at risk of reaching the 6-byte RBA or LRSN logging limits.
- The BSDS conversion increases the size of all log records, which accelerates progress toward the 6-byte RBA logging limit.
Db2 objects that remain in the 6-byte RBA format after Db2 reaches the soft logging limit (RBA x'FFF800000000') can cause updates to fail with reason code 00C2026D, and outages result because the objects become read-only until they are converted to the 10-byte format.
RBA values greater than x'F00000000000' indicate a risk of reaching the 6-byte logging limit. If a non-data-sharing Db2 subsystem is already at risk of reaching the 6-byte RBA, it is best to convert the pagesets for Db2 catalog and directory objects first, and then convert the pagesets for all user objects, all before converting the BSDS.
In Db2 data sharing however, it's always best to convert the BSDS first, before converting the pagesets for other objects. Also, as long as the the data sharing group is not at risk for reaching the 6-byte LRSN limit—which is rare and occurs only with advanced LRSN delta values—you can you can avoid outages from any single member reaching the 6-byte RBA limit by converting the just the BSDS of that member to the 10-byte format.
For more information, see What to do before RBA or LRSN limits are reached.
For an in-depth overview of the 10-byte RBA and LRSN, download the Extended LRSN and RBA format support in IBM Db2 for z/OS white paper.