The primary function of the transaction log file is to:
- Record all changes to the database
- Record changes sequentially
- All data is written to the transaction log file first before committing the changes to the data file
- A triggering mechanism, called a checkpoint, is triggered each few minutes to the transaction log to indicate that a particular transaction has been completely written from the buffer to the data file; this process keeps flushes out the committed transaction, and maintains the size of the physical transaction log file (only in simple recovery mode)
- Key object needed to restore databases
- Controls the size of the transaction log file and prevents the log consuming the disk space
- Used in log shipping, database mirroring, and replication
- Allows recover to a point in time