Services
* The Log Writer: Updates the online redone logs. It creates local archived logs and transmission of the redologs to the standby.
* The Archive Process: Copying of the online redone logs for the standby bases in a remote or localized manner.
* The Fetch Archive Log: When managing archived logs for customers with multiple standby databases, each fetch request is serviced by a dedicated server on the primary database. So, if a customer has several standby databases, each fetch archive log request is handled by its own server on the primary database.
* Log Network: It gets used on the primary database to establish a connection with that of standby.
There are four services required on the standby:
* Fetch Archive Log: The archived redo files get pulled from primary sites. The transfer of the archived redo files is initiated on the detection of a sequence gap.
* Remote File: The Primary database is used to receive the archived or standby redo logs. You can get both the archived and the standby logs together as well.
* Archive Process: The standby redo logs that get applied by managed recovery are archived by this service. 4. Managed Recovery: The archived redo log details are applied to the standby database.
It controls the automated transfer of redo data from the production database to one or more archival destinations.
Redo transport services perform:
* Transmit redo data from the primary system to the standby systems in the configuration.
* Manage the process of resolving any gaps in the archived redo log files due to a network failure.
* Automatically detect missing or corrupted archived redo log files on a standby system and automatically retrieve replacement archived redo log files from the primary database or another standby database.
* In general, log apply services wait for the full archived redo log to arrive at the Oracle instance host before applying to the standby database.
* Redo data is received by the remote file server process (RFS) on the standby system, where the RFS process writes the redo data to either archived redo logs or optionally to a standby redo log.
* If a standby redo log is used, real time apply can be enabled, which allows Data Guard to recover redo data from the current standby redo log as it is being filled by the RFS process.
* Benefit? It has the benefit of quicker switchover, instantly updating results after a physical Oracle instance is changed to read-only with up-to-date reporting from a logical standby database.
ALTER DATABASE RECOVER MANAGED Oracle instance USING CURRENT LOGFILE;
Redo data is received by the remote file server process (RFS) on the standby system, where the RFS process writes the redo data to either archived redo logs or optionally to a standby redo log.
However, if you use a standby redo log, you can optionally enable real time apply, which allows Data Guard to recover redo data from the current standby redo log as it is being filled by the RFS process.
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