UV 14.2.1 uvconfig N_GLM_SELF_BUCKET setting

The lock table structures have now been taken from UniData and the recommendation I have followed and provided to UniData customers (and has been successful) for a long time is to use "the closest prime number to the maximum number of locks per transaction" — the per-process lock table (PTLT) is a flat hash, so one bucket per expected lock gives ~1 entry per chain. 

As noted the value must be prime. UniData (and I suspect UniVerse does this is as well) doesn't just warn — it silently rounds up to the next prime. So Entering 5000 yields 5003 anyway, plus the startup message "N_GLM_SELF_BUCKET should be a prime number". (4999 is also prime and technically 1 closer, but 5003 matches what the engine resolves to and avoids the warning.

There is a companion tuneable to look at — GLM_MEM_ALLOC should be max locks per transaction × 2, i.e. 10000.

Cost / caveats

Shared memory: NUSERS × N_GLM_SELF_BUCKET × 8 bytes in the control segment. At 5003 that's ~40 KB per user — 100 users ≈ 4 MB, 500 users ≈ 20 MB.
Don't inflate it beyond the real maximum. Unlock-all, transaction cleanup and lock-dump paths do a full scan of all buckets per call so 5003 buckets means 5003 iterations each time regardless of how many locks are actually held.

Thanks for those details ​@Jonathan Smith .

The extra info about needing the next higher prime is very helpful.