Additional considerations for the partition definition control blocks

When making changes to HALDB partition definitions, until the online partition definition control blocks are rebuilt, a number of circumstances could occur that you should be aware of.

Consider the following points:

• If you use a HALDB partition selection exit routine, you must issue either the /DBRECOVERY command or the UPDATE STOP(ACCESS) command and then, after making the changes to the partition definition, the /START command or the UPDATE START (ACCESS) command. When the HALDB partition selection exit routine selects a HALDB partition, IMS is not aware of HALDB partition boundaries until the internal partition definition control blocks are finished being rebuilt.
• If you are using a HALDB partition selection exit routine and IMS notifies you of a structure modification, you might need the exit routine to select partitions correctly based on the current partition structure.
• A /START DB partition_name OPEN command might fail after the definition of a partition structure is changed because the corresponding partition definition control block needs to be rebuilt. To invoke a rebuild of the control block, an application program that uses the partition must be run or the type-1 command /START DB HALDB_Master OPEN must be issued.
• Newly added partitions are not known by the online IMS system until a rebuild of the corresponding partition definition control blocks has been invoked and the new control blocks have been created.
• If you are using a partition selection exit routine, be sure that it contains code that processes the structure initialization and structure modification calls that IMS issues when updating partition definition control blocks after partitions are added or modified. The sample Partition Selection exit routine (DFSPSE00) delivered with IMS includes code that supports these calls.