- No more than 512 SP's in a WLM
Let me explain why I recommend this. It's actually at the bottom of the list, and that's because it doesn't come up that often. But it has, and when it does, it can cost in I/O. DB2 has a Language Environment table of load modules in each stored procedures address space. For stored procedures defined STAY RESIDENT YES, we only have room for 512 load modules in that table. A load module has to be in the table in order for DB2 to invoke it. So, starting with the 512th, we'll delete it from the table after we call it, even if it's STAY RESIDENT YES. And come to think of it, we have separate tables for TYPE MAIN and TYPE SUB.
So to be completely accurate, the recommendation could actually say something like this:
- No more than 512 different load modules for STAY RESIDENT YES SP's in a WLM application environment, that are all either PROGRAM TYPE MAIN or PROGRAM TYPE SUB and invoked during the lifetime of a single instance of a WLM-SPAS.
For that last bit, remember that different invokers of a stored procedure that end up classified in different WLM enclaves will not have their SPs run in the same instance of a WLM-SPAS.
What's a WLM-SPAS? It's what I use to abbreviate a "WLM-established stored procedures address space".
And this post has motivated me to get a more recent copy of my stored procedures recommended practices presentation out online!