Thread Management

The thread management parameters that are set during installation controls how many threads can be connected to DB2 and it also determines the main storage size needed. Improperly allocating these parameters during installation directly affects main storage usage. If the allocation is too high, storage is wasted. If the allocation is too low, performance degradation occurs because users are waiting for available threads.

You can use a DB2 performance trace record with IFCID 0073 to retrieve information about how often thread create requests wait for available threads. Starting a performance trace can involve the substantial overhead, so be sure to qualify the trace with specific IFCIDS, and other qualifiers, to limit the data collected.

The MAX USERS field during installation specifies the maximum number of allied threads that can be allocated concurrently. These threads include TSO users, batch jobs, IMS, CICS, and tasks using the call attachment facility. The maximum number of threads that can be accessing data concurrently is the sum of this value and the MAX REMOTE ACTIVE specification. When the number of users trying to access DB2 exceeds your maximum, plan allocation requests are queued.