Question

In Sql Server, I find that, when I mark a database as read only, its existing large transaction log remains. To fix this I have to set it back to writeable, then dbcc shrinkfile on the log file, then set it read-only again.

What is the use of a transaction log if the database is read only? Is there a reason it doesn’t just get deleted/flushed?

Answer 1

If your database is still in full recovery mode, the log will not shrink without a proper backup. You should switch your read-only database to simple recovery.

Also, the log file is needed should you ever decide to detach/attach this database. As noted here:

In contrast, for a read-only database,
the log cannot be rebuilt because the
primary file cannot be updated.
Therefore, when you attach a read-only
database whose log is unavailable, you
must provide the log files or files in
the FOR ATTACH clause.