Sql-server – SQL Server 2008 DB size grown huge

"Shrinking" the log is actually "clearing" the log.

The log is basically a list of operations that have been performed, and is used as a reference for rollbacks, restores, checkpoints, etc.

The space wasn't "unused" but it contained transactions that had been committed and were reflected in the backup that was performed.

Your boss cleared out all the transactions in the log file, but since you had just run a backup this is acceptable since none of those transactions were uncommitted.

Even with the SIMPLE recovery model, the trans log can still blow up if there's a long running transaction going on. I'm wondering if something on your Dev server was running while your script was doing its thing and cause the trans log to not be able to truncate since the MinLSN was from some long running transaction.

To answer the question though, unless you restrict access to the DB (like running your script using ALTER DATABASE SET RESTRICTED_USER WITH ROLLBACK IMMEDIATE or something similar like SINGLE_USER), there's no way you can force the log file to free space as other transactions may be running and the trans log has to stay consistent for those transactions.

Check TechNet (or BOL: Checkpoints and the Active Portion of the Log) for more information.