Re: I/O performance of SQL SEQUENCE objects

Hi Dieter,

Lol...I recall those conversations. Shouldn't be an issue, as a GUID would
only have to be unique within the machine.

Replacing the use of a sequence object with our own data area is an
option. Though the question is, can a straight RPG program perform the
operation faster than the DB can with a SEQUENCE?

I'd like to think IBM's optimized the SEQUENCE object and that RPG can't do
it any faster; but I suspect that may not be the case. I've just never
seen any benchmarks.

Also, I was passed copy of a presentation, "Warpspeedlocking" presented by
Ed Prosser of IBM talking about some stuff added in v5r3 that may provide a
better alternative.
V5R3+:
– New atomic MI instructions
– CHKLKVAL/CLRLKVAL: low-level locking
– Lightweight CMPSWP option

Charles

On Sat, Feb 18, 2017 at 12:17 AM, D*B <dieter.bender@xxxxxxxxxxxx> wrote:

first of all, I would be very carefull with the GUID approach. we've had a
discussion about "most likely unique" 14 years ago.
I don't understand the problem, you described, in detail. caching in a
sequence works well for getting multiple numbers in the same job and is
useless for many jobs getting their first sequence number at the same time.
For the first case it would be sufficient to replace the sequence by a
SRVPGM with your own getNextId function, backed up by a table, caching some
numbers. For the second case, I would simply use a compound of jobnumber
and number of request, this would be fastest anyway.

D*B
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