Kbase P47010: What is the recommended value for -aibufs?
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/16/2008 |
|
Status: Verified
GOAL:
What is the recommended value for -aibufs?
GOAL:
What should the after-image buffers (-aibufs) database startup parameter to be set to
GOAL:
Why are ai notes a bottleneck with Fathom Replication enabled databases
FIX:
When a Progress database is after-image enabled, we recommend the after-image buffers (-aibufs) database startup parameter to be set to a value of 1.5 times the database tuned value of the Before-image Buffers (-bibufs) parameter. The after-image writer (AIW) process also needs to be running to assume the task of writing the ai buffers from the broker process, and the ai blocksize must equal the bi blocksize, othwerwise any gain from increasing the number of ai buffers is negligible.
As with any optimim performance tuning, this implies an Enterprise database license.
In the case of Fathom Replication the need for "ai tuning" is more apparent because there are additional ai notes required by Replication. Each record created/updated/deleted is performed within a logical operation. A logical operation being a unit of work within a transaction, that insures that a record and it's index entries are updated as a unit. The additional notes describe the beginning and end of each logical operation. The Replication Agent (RPLA) uses these to perform low-level record-get locks. Record-get locks prevent half updated records from being retrieved by 4GL or SQL.
As writes to the ai notes are buffered, fixed ai extents as opposed to variable ai extents will further improve the situation.