Common storage

Each WebSphere MQ for z/OS subsystem has the following approximate storage requirements:

• CSA 4 KB

• ECSA 800 KB, plus the size of the trace table specified in the TRACTBL parameter of the CSQ6SYSP system parameter macro. This macro is described in the WebSphere MQ for z/OS System Setup Guide.

In addition, each concurrent WebSphere MQ logical connection requires about 5 KB of ECSA. When a task ends, other WebSphere MQ tasks can reuse this storage. WebSphere MQ does not release the storage until the queue manager is shut down, so we can calculate the maximum amount of ECSA required by multiplying the maximum number of concurrent logical connections by 5 KB. Concurrent logical connections are the number of:

• Tasks (TCBs) in Batch, TSO, USS, IMS and DB/2 SPAS regions that have connected to WebSphere MQ, but not disconnected.

• CICS transactions that have issued a WebSphere MQ request, but have not terminated

• JMS QueueSessions that have been created (for bindings connection), but not yet destroyed or garbage collected.

• Active WebSphere MQ channels.

The channel initiator typically requires ECSA usage of up to 160 KB.