Sql-server – Manually set log file size after shrink SQL Server 2008 R2

sql-server-2008transaction-log

Am becoming a somewhat involuntary DBA at work at themoment and really need some help on something.

We have a 40GB database in Full Recovery Mode, no log backup configured and a huge log file of 84GB. My plan thus far to salvage this situation is to run a full log backup on the database, shrink the log file and instigate a maintenance plan to run a log backup every night with the database backup to help keep it under control.

My problem is I do not want the log file to shrink down to nothing and spend the first morning on Monday constantly growing. I have a rough estimate as to what the file should be (about 20% of the database) and would like to set this from the get-go to ensure as much contiguous space as possible. Is this just a case of changing "Initial Size" under database Properties -> Files? I would guess as well that the database would need to be offline for this to occur?

Thanks in advance

Best Answer

Just shrink to what you think is the optimal size. Don't use the UI, just do this - let's say 200 MB is your optimal size:

USE yourdb;
GO
DBCC SHRINKFILE(yourdb_log, 200);

If you're only interested in taking a log backup once a day, and aren't interested in point-in-time recovery, then you should switch to simple recovery model. This will mean log backups are unnecessary (in fact impossible) but the contents of the log will self-manage.

If you want log backups to be meaningful, don't plan on taking a full backup at night and then a single log backup right after. This keeps you in full recovery model, makes the log work really hard, and doesn't buy you anything. So if you want point-in-time recovery, run log backups more frequently at a rate that satisfies your data loss tolerance. If you don't ever want to lose more than 15 minutes of data, run a log backup every 15 minutes.

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