【DATAGUARD】Data Guard Wait Events

This note describes the wait events that monitor the performance of the log 
transport modes that were specified on the primary database with the ARCH, LGWR,
SYNC, and ASYNC attributes on the LOG_ARCHIVE_DEST_n initialization parameter. 
The wait events and associated timing information are displayed by the 
V$SYSTEM_EVENT view, as follows: 


Wait events for standby destinations configured with the ARCH attribute: 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

"ARCH wait on ATTACH" 

	This wait event monitors the amount of time spent by all archiver 
	processes to spawn an RFS connection. 

"ARCH wait on SENDREQ"

	This wait event monitors the amount of time spent by all archiver 
	processes to write the received redo to disk as well  as open and close 
	the remote archived redo logs. 

"ARCH wait on DETACH" 

	This wait event monitors the amount of time spent by all archiver 
	processes to delete an RFS connection. 
  

Wait events for standby destinations configured with the LGWR SYNC attributes: 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

"LGWR wait on ATTACH" 

	This wait event monitors the amount of time spent by all log writer 
	processes to spawn an RFS connection. 

"LGWR wait on SENDREQ"

	This wait event monitors the amount of time spent by all log writer 
	processes to  write the received redo to disk  as  well as open and close
	the remote archived redo logs.
 
"LGWR wait on DETACH"

	This wait event monitors the amount of time spent by all log writer 
	processes to delete an RFS connection. 


Wait events for standby destinations configured with the LGWR ASYNC attributes:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

"LNS wait on ATTACH" 

	This wait event monitors the amount of time spent by all network servers
	to spawn an RFS connection. 

"LNS wait on SENDREQ"

	This wait event monitors the amount of time spent by all network servers
	to write the received redo to disk  as well  as open and close the remote
	archived redo logs.

"LNS wait on DETACH"

	This wait event monitors the amount of time spent by all network servers
	to delete an RFS connection.
 
"LGWR wait on full LNS buffer" 

	This wait event monitors the amount of time spent by the log writer 
	(LGWR) process waiting for the network server (LNS) to free up ASYNC 
	buffer space. If buffer space has not been freed in a reasonable amount 
	of time, availability of the primary database is not compromised by 
	allowing the archiver process (ARCn) to transmit the redo log data. This
	wait event is not relevant for destinations configured with the LGWR 
	SYNC=PARALLEL attributes. 
  

Wait events for standby destinations configured with either the LGWR ASYNC or 
LGWR SYNC=PARALLEL attributes: 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

"LGWR wait on LNS"

	This wait event monitors the amount of time spent by the log writer (LGWR)
	process waiting to receive messages on KSR channels from the network 
	server. 
        
"LNS wait on LGWR"

	This wait event monitors the amount of time spent by the network server 
	waiting to receive messages on KSR channels from the log writer (LGWR) 
	process. 

"LGWR-LNS wait on channel"

	This wait event monitors the amount of time spent by the log writer (LGWR)
	process or the network server processes waiting to receive messages on 
	KSR channels.