Channel initiator private region storage usage
Every channel uses approximately 170 KB of extended private region in the channel initiator address space. Storage is increased by message size if messages larger than 32 KB are transmitted. This increased storage is freed when:
- A sending or client channel requires less than half the current buffer size for 10 consecutive messages.
- A heartbeat is sent or received.
The storage is freed for reuse within the LE environment, but is not seen as free by the z/OS virtual storage manager. This means that the upper limit for the number of channels is dependent on message size and arrival patterns as well as on limitations of individual user systems on extended private region size. The upper limit on the number of channels is likely to be approximately 9000 on many systems because the extended region size is unlikely to exceed 1.6 GB. The use of message sizes larger than 32 KB reduces the maximum number of channels in the system. For example, if messages that are 100 MB long are transmitted, and an extended region size of 1.6 GB is assumed, the maximum number of channels is 15.