Processing option P (PROCOPT=P)

The PROCOPT=P option is specified during the PCB generation in the PCB statement or in the SENSEG statement for the root segment.

The option takes effect only if the region type is a BMP. If specified, it offers the following advantage:

Whenever an attempt is made to retrieve or insert a DEDB segment that causes a UOW boundary to be crossed, a 'GC' status code is set in the PCB but no segment is returned or inserted. The only calls for which this takes place are: G(H)U, G(H)N, POS, and ISRT.

Although crossing the UOW boundary has no particular significance for most applications, the 'GC' status code that is returned indicates this could be a convenient time to invoke sync point processing. This is because a UOW boundary is also a CI boundary. As explained for sequential processing, a CI boundary is a convenient place to request a sync point.

The sync point is invoked by either a SYNC or a CHKP call, but this normally causes position on all currently accessed databases to be lost. The application program then has to resume processing by reestablishing position first. This situation is not always easy to solve, particularly for unqualified G(H)N processing.

An additional advantage with this processing option is, if a SYNC or CHKP call is issued after a 'GC' status code, database position is kept. Database position is such that an unqualified G(H)N call issued after a 'GC' status code returns the first root segment of the next UOW. When a 'GC' status code is returned, no data is presented or inserted. Therefore, the application program should, optionally, request a sync point, reissue the database call that caused the 'GC' status code, and proceed. The application program can ignore the 'GC' status code, and the next database call will work as usual.

Database recovery and change accumulation processing must buffer all log records written between sync points. Sync points must be taken at frequent intervals to avoid exhausting available storage. If not, database recovery might not be possible.