Transaction log has huge growth after backup

Question

I am a programmer, with a side job as an involuntary DBA.

I have a maintenance plan that does a full backup and a 'check database integrity' every night. I backup transaction logs every 10 minutes. The transaction log backup size spikes after the database backup - exponentially bigger. I used to rebuild indexes and statistics every night - I thought that is what was causing the transaction log spike - but removing those steps didn't change anything.

Mirroring our backups on slow connections would be helped considerably if there wasn't this massive spike - so I am hoping it is something I am doing wrong. Can anyone suggest anything?

Answer 1

While your full backup is running, transaction backups will not run. So how long does your full backup take? The transaction log will not be truncated during this time by transaction log backups.

Answer 2

Is this SQL 2000?

In SQL 2000, you're not supposed to run the log backup while the full backup is executing, or "bad things can happen", like blocking, or hugely bloated log files.

See this ServerFault post for "The Word" from "The Man", Paul Randal, who used to be in charge of the SQL engine at Microsoft.

See this follow-up post for some ideas for skipping the log backup while the full backup is executing.

In SQL 2005 or later, this restriction no longer exists, and you shouldn't have trouble running log backups and full backups at the same time.

Answer 3

If you are only running the log backup from 6am to midnight, then the very first log backup at 6am is backing up all the database activity that has occurred in the 6 hours since the last log backup.

This is entirely normal, and probably has nothing to do with the fact that your database backup takes place at 4am.

Since you are on SQL2008, the warning in my other answer doesn't apply, and you should be fine with running the log backups 24 hours.