SQL Server transaction log backups,
- by krimerd
Hi there, I have a question regarding the transaction log backups in sql server 2008. I am currently taking full backups once a week (Sunday) and transaction log backups daily. I put full backup in folder1 on Sunday and then on Monday I also put the 1st transaction log backup in the same folder. On tuesday, before I take the 2nd transaction log backup I move the first transaction log backup from folder1 an put it into folder2 and then I take the 2nd transaction log backup and put it in the folder1. Same thing on Wed, Thurs and so on. Basicaly in folder1 I always have the latest full backup and the latest transaction log backup while the other transaction log backups are in folder2. My questions is, when sql server is about to take, lets say 4th (Thursday) transaction log backup, does it look for the previous transac log backups (1st, 2nd, and 3rd) so that this new backup will only include the transactions from the last backup or it has some other way of knowing whether there are other transac log backups. Basically, I am asking this because all my transaction log backups seem to be about the same size and I thought that their size will depend on the amount of transactions since the last transaction log backup.
Example:
If you have a, lets say, full backup and then you take a transac log backup and this transac log backup is lets say 200 MB and now you immediatelly take another transac log backup, this last transac log backup should be considerably smaller than the first one because no or almost no transaction occured between these two backups, right? At least, that's what I've been assuming. What happens in my case is that this second backup is pretty much the same size as the first one and I am wondering if the reason for that is because I moved the first transac log backup to a different folder so now sql server thinks that all I have is just a full backup and it then gets all the transactions that happened since the full backup and puts it in the 2nd transac log backup.
Can anyone please explain if my assumptions are right? Thanks...
