probkup online and offline

[billduty]

Running the following commands

probkup online db-name db-name.bk01 -com

probkup db-name db-name.bk01 -com


The offline backup is 5GB and the online backkup is 7.6GB consistently.

Progress 10.1A Linux box.

Anyone know why the backups are different sizes? Does the online store more info??

 

[Cringer]

Something to do with the BI files?

 

[TomBascom]

When you are online you are still making changes to the db -- the online backup has to account for that. Anything that changes after the backup starts must be written to the backup. Possibly more than once.

2.6GB sounds like a lot but maybe you have a fairly busy system.

 

[tamhas]

Anything that changes after the backup starts must be written to the backup. Possibly more than once.

Is that correct??? I thought that the online backup was a copy as of the *start* of the backup. And that if there were commits after the backup started, that it backed up the image *before* the commit and then did the commit.

That might mean backing up things out of order which might imply more "notes" in the backup file. Still, 2.6GB sounds like a lot.

 

[RealHeavyDude]

Anything that changes after the backup starts must be written to the backup. Possibly more than once.

I always thought that the online backup works the following:

• Backup all database blocks sequentially.
• A database block further down the road should be updated.
• Suspend the update until the block concerned is backedup.
• Jump to that block and back it up.
• Jump back to where it was before backing up the block to-be-updated.
• Continue to backup the blocks sequentially.

If that is true, then the changes after the backup started are not pare of the backup as it is a snapshot of the database at the time the backup started. Or am I missing something?

Heavy Regards, RealHeavyDude.

 

[TomBascom]

I was talking out my butt. Dr. Hursh and RHD are correct. I plead insufficient coffee, and sentence myself to a fresh cup

If a block is updated after the backup starts the block being modified must first be written to the backup.

Which leaves the bi file as the largest likely contributor to differences in backup size.

 

[tamhas]

Which raises the question ... just how large *is* the BI file on this DB?

 

[billduty]

As of a couple minutes ago the bi was 172MB. I did maintenance on the clients db this weekend and noticed the difference where they store the backups. Weekends db's are shutdown and backed up and weekdays are online. I didn't check the script to see if they've truncated the db. I'll keep an eye on the BI to see if it get's larger.

 

[RealHeavyDude]

Just my 2 cents: AFAIK, the backup, regardless whether taken off- or online, only backs up the used database blocks. In our production system I found a database where the same is true - but there is a business case which is responsible for that: Starting Monday morning tons of data get imported from several providers. During the week end processing which runs Friday night these data gets reconciled - which obviously removes lots of data. In that case it does make sense that the offline back that runs during the night from Saturday to Sunday is smaller than the online backups taken during the week - they constantly grow until the end of the week.

I am not 100% positive what the compression ( -com ) really does, but it might add up.

Heavy Regards, RealHeavyDude.

 

[TomBascom]

-com skips empty space in the db. It does not do any "zip" style compression.

 

[billduty]

OK - This mornings backup is 5.2GB with an online backup and a small BI (172 MB). This past weekend I backedup, prodelete, and restored into a new structure file with some larger storage areas - so we had a new BI file. Thanks for all of the input.