PRIORITY is a parameter of the DB2CONN and DB2ENTRY definitions of the CICS-DB2 attachment facility. It can be specified for both pool and entry threads. The PRIORITY parameter controls the priority of the thread TCBs relative to the CICS® main TCB (QR TCB). If CICS is connected to DB2® Version 6 or later, the thread TCBs are CICS open L8 TCBs. If CICS is connected to DB2 Version 5 or earlier, the thread TCBs are private subtask TCBs created by the CICS-DB2 attachment facility. There are three options: PRIORITY=HIGH, PRIORITY=LOW, and PRIORITY=EQUAL. (See the CICS Resource Definition Guide for more information.)
When PRIORITY=HIGH is specified, transactions run at a higher priority than CICS, thus saving virtual storage, releasing locks, and avoiding other transactions deadlocking or timing out. However, if all threads are specified with PRIORITY=HIGH, CICS itself may be effectively at too low a priority.
Setting PRIORITY=HIGH is useful for high-priority and high-volume transactions.
A complex SQL call could spend a long time in DB2, and the CICS TCB may not be dispatched.
Set PRIORITY=HIGH for your transactions with the highest weighted average number of SQL calls. The highest weighted average is equal to the number of SQL calls per transaction multiplied by the frequency of transaction. Set PRIORITY=LOW or EQUAL for other transactions. If the CPU usage per call is high, you should not set PRIORITY=HIGH.
PRIORITY is a parameter of the DB2CONN and DB2ENTRY definitions of the CICS attachment facility.
The following facilities are available to monitor CICS attachment facility.