Ask the Expert

How does the Oracle LGWR write to online redo log files?

How does the Oracle LGWR write the log buffer to the online redo log? Does it write out the entire log buffer or just the committed records? If it writes out just the committed records, would it increase 'log file parallel write' time for using a large log buffer?

    Requires Free Membership to View

LGWR does write change records in the log buffer to the online redo log files. When a user issues a COMMIT, the COMMIT is not complete until the change records have been written to the online redo logs. However, large transactions may fill the log buffer before a COMMIT is issued. For this reason, LGWR will write to the online redo logs if the log buffer becomes one-third full or after there is 1MB of new redo in the log buffer, or every 3 seconds, or before DBWn writes to the database files. As you can see, LGWR does not write just committed transactions, it may write uncommitted ones as well.

This was first published in November 2009

There are Comments. Add yours.

TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: