This parameter specifies the number of threads that are created when CICS® connects to DBCTL. They remain allocated while the database resource adapter (DRA) is active. These threads continue to remain allocated until the CICS system is disconnected from DBCTL, unless a thread is stopped by a /STOP command or by a thread failure.
The DRA allocates control blocks for the specified number of threads at DBCTL connection time. One thread is equivalent to one MVS™ TCB, thus giving more concurrency on multiprocessors. Because these threads are available for the duration of the DBCTL connection, there is no pathlength overhead for collapsing and reallocating thread related storage, and throughput should, therefore, be faster.
The number you specify should be large enough to cover average DL/I transaction loads. After the MINTHRD limit is reached, additional threads are allocated up to the MAXTHRD limit, the number specified in the MAXREGN, or the maximum of 255, whichever is the lowest.
When multiple CICS systems or Batch message processing programs (BMPs) are connected to DBCTL, the sum of MINTHRD and BMPs must be less than or equal to MAXREGN (MAXREGN is specified in the IMS™ sysgen macros).
MINTHRD can be used in DBCTL systems to synchronize thread allocation with workload requirements.
There is a storage allocation of about 9KB per thread in the local system queue area (LSQA) below the 16MB line.
The MINTHRD and MAXTHRD parameters are specified in the DRA startup table (DFSPZP).
DBCTL statistics are available when the CICS/DBCTL interface is shut down normally. The MINTHRD value is recorded (see DBCTL session termination statistics for further information). You can also use CICS auxiliary trace to check for queueing for threads and PSBs.