This page describes deployment use cases when there are multiple Oracle standby database for one Oracle primary database. Each synchronization pair is a separate DDC configuration. Dbvisit StandbyMP supports Parallel and Cascade mode for multiple standby databases.
If failover occurs for any standby database due to real-DR event (regardless whether parallel or cascade), all other databases part of one-to-many configurations must be recreated from the scratch as standby databases.
A. Parallel
There is no limit to number of standby databases synchronized from a single primary database
Parallel configurations have single primary as source for archivelog synchronization and synchronization is done in parallel to multiple standby databases. For example:
Where:
DDC1 = Synchronization from Primary Database to Standby A
DDC2 = Synchronization from Primary Database to Standby B
DDC3 = Synchronization from Primary Database to Standby C
Each DDC is “usual” configuration
Each archivelog generated by primary database must be sent for each DDC separately
All parallel DDC configurations are independent on each other
If synchronization would fail for one DDC (for example due to network issue), other DDC synchronizations would be unaffected
There are no specific DDC parameters which would indicate relation between parallel DDC files. Each DDC file is independent. If there is a situation, when database role change for a single DDC configuration, other DDC configurations will remain unchanged. For example, if switchover is performed for DDC2, configurations DDC1 and DDC3 will stop working. Synchronization for these two configurations will not be possible until DDC2 is switched back to the original state or until remaining DDCs are manually reconfigured.
If Dbvisit StandbyMP AMM module is used for primary database (ARCHSOURCE Management), it must be enabled only on one of the configurations. It must be disabled on all other configurations
Before you start Switchover process for one of the configurations, make sure Automated Standby Update feature is turned off for other configurations. If there is any automated update active during the Switchover, the action fails in the early stage with ERROR_CODE:932.
B. Cascade
There is no limit to number of standby databases in cascade chain
Cascade configuration is special type of configuration, where source for archivelog synchronization is a standby database. Multiple cascade configurations create a chain where cascade DDC configurations are dependent on each other. First standby in the chain database is always a “usual” Dbvisit Standby database. Example:
Where:
DDC1 = Synchronization from Primary Database to Standby A and is “usual” DDC configuration
DDC2 = Synchronization from Standby Database A to Standby Database B and is special DDC cascade configuration
DDC3 = Synchronization from Standby Database B to Standby Database C and is special DDC cascade configuration
Each archivelog generated by primary database is sent only once from primary server. Archivelog which is applied to standby database A is then sent from standby database A to standby database B, where it will be applied to standby database B and so on.
Cascade DDC configurations are semi-independent on each other: each DDC in chain can become single point of failure. There are no specific DDC parameters which would indicate relation between cascade DDC files. If synchronization would fail for one DDC (for example due to network issue), synchronization for following DDCs in the chain will fail as well
It is not possible to perform switchover between standby databases. Following example above, switchover is disabled for DDC2 and DDC3.
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