Using extended common service area (ECSA)

The extended common service area (ECSA) is a major storage area above the 16 MB line, containing pageable system data areas addressable by all active virtual address spaces. Use of ECSA is based on the following formulas:

   #tasks_using_Openmvs * 150 bytes
   #processes * 500 bytes
   #dubbed_address_space * 500 bytes

For example, if your system supports 200 dubbed address spaces, 500 processes, and 2000 threads, the kernel service consumes an additional 650KB of ECSA.

In addition to this ECSA usage,

The workload manager (WLM) also uses some ECSA for each initiator to satisfy a fork request.
The OMVS address space uses an additional 20 KB of ECSA. The kernel also uses ECSA to process spawn requests. This storage is freed when no longer needed. Allocate an additional 100K of ECSA for spawn usage.
Each process that has a STEPLIB that is propagated from parent to child or across an exec will consume about 200 bytes of ECSA. If STEPLIBs are used for all processes and you have 400® processes, an additional 80K of ECSA is required.