WLM management of stored procedures

Workload Manager (WLM) is a component of z/OS® that manages incoming work requests for the operating system and allocates available system resources to meet these requests. DB2® for z/OS uses WLM to allocate workload requests for DB2 stored procedures.

When DB2 receives a request to run a stored procedure, WLM determines whether additional resources are needed to process the request. For example, WLM might determine that a new WLM-managed address space is needed. WLM makes this determination by evaluating whether the work for a service class is meeting the goals that you set. WLM also evaluates whether the work queues are becoming too large. WLM then examines the system resource utilization as part of the algorithm to decide if another address space should be started. In many cases, a sudden increase in incoming work is handled by existing WLM address spaces, and task control blocks (TCBs) remove work from the queues. Consequently, an address space can handle more concurrent stored procedures or user-defined functions than the number that is specified by NUMTCB in the application environment definition.

A WLM application environment starts and manages WLM address spaces that are to be used by stored procedures. You can either create your own WLM application environments or use existing ones, and each stored procedure must be assigned to a WLM application environment. You can assign more than one stored procedure to each WLM application environment, but you might want to separate them for various resource management reasons. The stored procedures that are assigned to a WLM application environment do not need to be written in the same high-level language. However, for different performance reasons, you might decide to separate stored procedures into different application environments by language.

You define application environments for stored procedures as part of your WLM service policy. You also need to define a JCL procedure that WLM is to use to start the address spaces. You store this procedure in PROCLIB. The application environment definition in your policy contains the name of this startup procedure in PROCLIB. If too few address spaces are available to meet the policy goal, WLM starts another server address space if the service policy definition allows it.