How does a large transaction log affect performance?

Question

If the transaction log file is full in the SQL Server database, it degrades the performance of the SQL Server. It also slows down the speed of the transactional log backup process. In addition, the over-sized transaction logs decrease the disk space also because old transaction logs are not removed yet. 4 апр. 2017 г.

What happens when transaction log is full?

When the transaction log becomes full, SQL Server Database Engine issues a 9002 error. The log can fill when the database is online, or in recovery. If the log fills while the database is online, the database remains online but can only be read, not updated.

Why is my transaction log file so big?

Large database transactions, such as importing large amounts of data, can lead to a large transaction log file. Transaction log backups not happening fast enough causes the SQL log file to become huge. SQL log files also enlarge due to incomplete replication or availability group synchronization.

Why is transaction log important?

A transaction log is used to record the fact that a transaction is set to occur as well as the information needed by the database server to recover the data back to a consistent state in event of a sever failure while it is writing information to disk.

What happens when the log file reaches its size limit?

If your log file reaches its limit in size during a transaction and cannot autogrow then the transaction won't be able to commit and you will see errors in SQL. The log file needs to be sufficiently sized to handle the transactions in between CHECKPOINT operations.

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