gtpd1m20Database Reference

Commit Scope Processing

The following information describes the file-type requests and MQSeries-type requests used for commit scope processing.

File-Type Requests

At a high level, file-type requests that are entered in a commit scope are cached by the TPF system in virtual file access (VFA). This affects the amount of storage used for VFA. When you enter a find-type request for a record that is written by a commit scope (or a higher-level commit scope if the commit scope is nested), the record is read from a special VFA buffer, called a commit scope buffer, instead of from a normal VFA buffer or from DASD.

Note:
Commit scope buffers do not age out of VFA.

The commit control records that are used by the transaction manager are maintained in system work blocks (SWBs); this will increase the number of SWBs that are required in the TPF system.

DASD hold processing is recorded in the commit control records for use when a commit transaction (tx_commit C function or TXCMC assembler macro) or rollback transaction (tx_rollback C function or TXRBC assembler macro) is entered. The record hold table (RHT) is used to maintain the following:

Specifying this as an external is intended to minimize updates to customer tools that recognize the record hold table.

MQSeries-Type Requests

At a high level, all processor unique queues are maintained in system heap and SWBs to obtain extremely high access rates to TPF queues. To assist with the recovery of persistent messages after an IPL, the contents of all queues are checkpointed on a time-initiated basis to fixed file records. All updates made by using the MQPUT, MQPUT1, or MQGET functions between checkpoints are written to the recovery log.

All processor shared queues are filed on TPF collection support (TPFCS).