Maintenance of data sharing groups

To apply maintenance, you can make most changes on one member at a time.

If you must take Db2, IRLM, or z/OS® offline for a change to take place and the outage is unacceptable to users, you can move those users onto another member. Some sites find it useful to define an extra member that they bring up and down as needed to take on work while maintenance is being applied to another member.

The recommended way of testing maintenance is to apply that maintenance to a test data sharing group before moving it onto the production data sharing group.

Table 1. Actions required for planned maintenance changes
Type of change	Action required
Early code	Issue the -REFRESH Db2,EARLY command.
Db2 code	Bring down and restart each member independently.
IRLM code	Bring down and restart each IRLM member independently.
Attachment code	Apply the change and restart the transaction manager or application.
Subsystem parameters	For those that cannot be changed dynamically, update using the Db2 update process. Stop and restart the member to activate the updated parameter.

Recommendation: Consider specifying CASTOUT(NO) when you stop an individual member of a data sharing group for maintenance. This option speeds up shutdown because Db2 bypasses castout and associated cleanup processing in the group buffer pools.

Do not specify CASTOUT(NO) when you stop multiple members of a data sharing group and you need to maintain consistent data on disk. For example, if you stop all members to get a consistent copy of the databases on disk that you can send offsite, do not specify CASTOUT(NO) because some of the changed data could still reside in the group buffer pools after the members shut down. Your disk copy might not have all the most recent data.

Tip: Consider specifying a value of NODISCON for the IRLM procedure's SCOPE option to allow IRLM to continue doing work while you apply maintenance to Db2. (If you edit the IRLM procedure using the Db2 installation process, this is analogous to specifying NO for parameter DISCONNECT IRLM on installation panel DSNTIPJ.)

Applying maintenance to IRLM: Each member of a data sharing group has its own IRLM. As with Db2, you must stop and restart each IRLM in the group to roll a change throughout the group.

IRLM has a function level to control changes that affect the entire group. The function level for a particular IRLM member indicates the latest function that IRLM is capable of running. The group function level is the lowest function level that exists among the IRLMs in the group. The group function level is the function level at which all IRLMs in the group must run, even if some IRLM members are capable of running at higher function levels.

Recommendation: Keep all members of the IRLM group at the same function level. This ensures that all IRLMs are running with the same maintenance that affects the entire group. (Maintenance that does not affect the group does not increment the function level.)

To see the IRLM function levels, use the MODIFY irlmproc,STATUS,ALLI command of z/OS.