Fixing a transaction log backup on an upgraded database

I created a new database and restored it from a SQL-Server 2000 system to SQL-Server 2005 with no problem. Then I set up a maintenance plan with two sub-plans: nightly full backups and hourly transaction log backups during the work day.

After setting up the backups I changed the database "Compatibility level" from 80 to 90. The nightly backup ran fine that night, but the transaction log backups failed consistently. Turns out that changing the database compatibility level wipes out the database's knowledge of when it was last backed up, and a transaction log backup will only run after a full backup. So I ran another full backup, and then transaction log backups started to run just fine.

The only useful error message, that pointed me to the real problem, was in the SQL-Server Integration Services Output file. The History log, the SQL-Server logs, and the server Event logs were pretty useless. So, always set up job step output files for every step, even if it seems unnecessary.