Datagaurd Quik Refference

Data guard setup and configuration - quick reference

Quick reference to dataguard configuration for the DBAs. The table gives an easy reference on the main attributes of log_archive_dest_n parameter and gives quick concept on the setting. Also, the scenarios where standby redo logs are used to minimize data loss and also to enable real-time apply is discussed.

Configuration	Performance	Availability	Protection	Meaning and Remarks
Standby redo logs	Not required, but recommended	Required	Required	Redo data from primary will be written to standby redo logs by LGWR process and real time apply can be enabled, LGWR/ARCH parameter can be set.
LGWR (Redo archival process)	Not required	Required	Required	Specifies the redo transport service uses LGWR to collect and transit redo data to standby.
ARCH (Redo archival process)	Possible	Not possible	Not possible	Specifies that redo transport services uses ARCn process to collect and transmit redo data to standby.
SYNC (Network transmission)	Not required	Required	Required	SYNC specifies Network I/O to standby is synchronous, that means the LGWR process on primary will wait for Network I/O to complete on the standby so that successful transfer of redo records to standby database is ensured.
ASYNC (Network transmission)	Can be set	Cannot be set	Cannot be set	ASYNC specifies the the LGWR will not wait for Network I/O  to complete and proceeds asynchronously. Not valid if ARCH parameter is used
AFFIRM (Disk Writes)	Not required	Required	Required	Specifies that disk I/O to archived redo logs and standby redo logs on the standby are done synchronously and the LGWR process on primary will wait to continue its processing.
NOAFFIRM (Disk Writes)	Can be set	Cannot be set	Cannot be set	Specifies that disk I/O to archived redo logs and standby redo logs on the standby is done asynchronously and the LGWR process on primary will not wait to continue its processing.