Kbase P142596: Could increasing the frequency at which after image switches are performed cause any major impact?
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/13/2009 |
|
Status: Verified
GOAL:
Could increasing the frequency at which after image switches are performed cause any major impact?
GOAL:
Would increasing the frequency of ai switches cause the roll forward process to reach its' roll forward extent limit faster?
GOAL:
What is the affect of reaching the after image roll forward sequence limit?
FACT(s) (Environment):
All Supported Operating Systems
Progress 9.x
OpenEdge 10.0x
OpenEdge 10.1A
OpenEdge 10.1B
FIX:
Yes, by increasing the frequency of the after image switches and keeping everything else the same, the afterimage counter (sequence number) for the creation of after image extents will increase more rapidly. Progress has a limit (65535) using the sequence counter for rolling forward after image files on a restored copy of a database. An increased frequency of switches would cause this limit to be reached more rapidly. If this limit is reached, you will no longer be able to roll forward after image files on the backup copy of the database. The creation counter on the original database does not have this limit. So Progress can continue to do ai switches on the original database. An attempt to roll forward an after image file with a sequence number greater than 65535 on the backup database fails with:
Expected ai file number 1 but file specified is 65536 in sequence. (8119)
The sequence counter for the number of after image files rolled forward on the backup database has reached 65535 ( the limit) and the counter rolled over to -1 which now gets reported as the expected value of 1. That number does not match the current ai creation number which is 65536. These numbers are no longer in sync thus preventing any further roll forward of after image files on the backup copy of the database.
Note:The roll forward counter on the original database always remains at 1 since it is not involved with the roll forward process.
Stop after imaging on the original database using the command: rfutil dbname -C aimage end.
Then re-establish after imaging on your database.