Showing posts with label redo. Show all posts
Showing posts with label redo. Show all posts

Friday, August 13, 2010

Data Guard optimizing ASYNC redo transport by log buffer

Data Guard redo configuration asynchronous mode, the Log Network Server (LNS) process will attemp to read redo directly from the log buffer. If the redo to be sent is not found in the log buffer, then the LNS process will go to the Online Redo Log (ORL) to retrieve it. Size the log buffer so that LNS is always able to find the redo that is needs to send within the log buffer.
The log buffer hit ratio is tracked in the view x$logbuf_readhist. A low hit ratio indicates that the LNS is frequently reading from the ORL instead of the log buffer. If there are periods when redo transport is coming close, but is not quite keeping pace with your redo generation rate, consider increasing the log buffer size in Data Guard 11g to achieve a favorable hit ratio.