Maximum Performance : This mode is the default protection mode and the log transport service must use the ASYNC mode with the LGWR or ARCH attribute. with 11g, ARCH transport is not recommended because it doesn't offer any advantage in terms of performance, and offers less data protection. (ASYNC) Maximum performance doesn’t bother of standby database whether redo is been sent to standby or even received or even applied.. There are not so many changes with protection mode except Maximum availability in 12c. From 12c Maximum availability supports only AFFIRM earlier, now it supports to NOAFFIRM as well. Just changing of redo transport attributes doesn’t perform protection level, You have to manually convert protection mode. What are new changes in 12c? – Max availability The NET_TIMEOUT parameter allows the LGWR on the primary database to wait for the specified time in the parameter for the RFS on the standby server to send an acknowledgement to the LGWR on the primary database saying that the log has been applied to the standby database and finally commits the ongoing transaction. If the LGWR in primary does not receive the acknowledgement within the NET_TIMEOUT period, then it would go ahead with the commitment and starts behaving in as the Maximum Performance Mode. Once the standby is up, it automatically gets the logs from the online redo logs of the primary database.
The Maximum Availability mode is the data protection mode that has the ability to run as a Maximum Protection or Maximum Performance mode depending on the accessibility of standby databases. It guarantees 100-percent data protection during normal operation in the event that the primary database fails(until unless same time failure at the primary site and power is lost at the standby site) .
No data loss even if primary database fails, to reach the protection level the redo data needed to recover transaction must be written to both the online redo log and to the standby redo log at least one synchronized standby database before the transaction commits
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVAILABILITY;
NSS(11.2) - Acts as a slave for LGWR when SYNC transport is configured for a remote standby destination NSS(12.1) - Transfers redo from current online redo logs to remote standby destinations configured for SYNC transport
LNS - primary database LGWR process is writing redo to its ORL, a separate Data Guard process called the Log Network Server (LNS) is reading from the redo buffer in SGA and passes redo to Oracle Net Services for transmission to the standby database
RFS - Redo records transmitted by the LNS are received at the standby database by another Data Guard process called the Remote File Server (RFS). The RFS receives the redo at the standby database and writes it to a sequential file called a standby redo log file (SRL).
At least one standby I able to transmit redo and the other standby(cascade) am not much worried because my data is safe in at least one standby Avoided network trip between primary to standby databases But I need huge storage in case of VLDB
Database = control + data files + redo , Instance = Memory + Back Ground processes, Semi Database – far sync
Far sync instances are part of the Oracle Active Data Guard Far Sync feature, which requires an Oracle Active Data Guard license. offload the primary database performance obligations/complexity and overcome network latency issues involved while shipping the redo synchronously to its all remote standby databases configured far away, at the same time guarantee zero data loss failover capabilities. - cannot perform any switchover or either failover operations
Supports up to 29 remote destinations
If your redo rate 8738133 bytes per second , bandwidth is 100 Mbps
Standby servers doesn’t mean that failover performed to different location, its just logical representation that we performed failover and now the database is new primary
Why VALID_FOR used STANDBY_LOGFILE,STANDBY_ROLE used from far sync to standby? The redo_log_type keyword identifies the destination whether valid or not.
For real-time apply, no need to start recovery using “current logfile”, real-time apply is enabled by default.
Standby can be
Oracle12c data guard farsync and whats new
Oracle 12c Data Guard –
Far Sync and what’s new
Author & Presenter: Nassyam Basha