Kbase 20987: FAQ on Progress On-line Backup (Probkup)
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
02/03/2009 |
|
Status: Verified
GOAL:
FAQ on Progress on-line backup (probkup)
GOAL:
How long does it take to write the header information using Progress on-line backup (probkup)?
GOAL:
How does Progress handle a database update AFTER the online backup has begun and header information has been written?
GOAL:
Is it necessary to initiate a quiet point during a Progress online backup?
FACT(s) (Environment):
All Supported Operating Systems
Progress 9.x
OpenEdge 10.x
FIX:
Q: How long does it take to write the header information?
A: The time is not noticeable when going to disk. With tape, it might be noticeable, especially if you have to switch tapes and the backup must wait for the new tape to be inserted. Also, online backup blocks updates while the bi log contents are being written.
Q: How does Progress handle a database update AFTER the online backup has begun and header information has been written?
A: The backup keeps a cursor that indicates how far it has proceeded. This cursor starts at the first database block and moves up as each block is backed up, until it gets to the high water mark (the last database block containing data). In the absence of any database changes, all the blocks would be written sequentially, one after another.
When another process wants to change a database block during the backup, if the block to be changed is below the backup cursor, it has already been backed up and can be changed as needed. If the block is above the backup cursor, then it must be backed up *before* it is changed. In this case, the block is placed on a queue and the process that wants to change it blocks, waiting for it to be written to the backup medium.
The backup program checks the queue before moving the cursor up and writes any blocks on the queue before doing anything else. When a block is written from the queue, the process waiting for it is notified and can then proceed to change it.
After the queue has been emptied, the backup program goes back to moving the cursor up and backing up blocks in sequence, checking the queue again each time.
Q: Is it *highly* recommended to initiate a quiet point during a Progress online backup?
A: It is not necessary to initiate a quiet point when doing a Progress On-line backup. The reason we added this feature is so that you can do a backup by splitting mirrors when you use mirrored disks. If you are using online backup, you don't need to do it.