1) Primary and Standby:
Primary Database
-- Production (Read & Write)

Standby Databases
-- Secondary (Mount, Open Read Only and Read Write)

2) The types of standby databases:
Physical standby database (Redo Apply - Open Read Only)
-- Allows use of the Oracle Active Data Guard option read-only and Open mode.
-- Switchover and/or failover operations are permitted

Logical standby database (SQL Apply - logical SQL statements - Open read Write)
-- Open for user access while applying changes
-- Logical standby tables can be open for SQL queries (read only),
and all other standby tables can be open for updates.

Snapshot Standby Database (No Redo Apply - Open Read Write)
-- Guaranteed restore point
-- Switchover and/or failover operations are not permitted

3) Oracle Data Guard Services:
Redo Transport Services
-- Production to archive destination (Standby)
-- Manage the process of resolving any gaps
-- Automatically detect missing or corrupted archived redo log files
on a standby system and automatically retrieve replacement

Apply Services
-- Redo Apply
-- SQL Apply

Role Transitions
-- Switch Over
-- Failover

4) Oracle Data Guard Protection Modes
Maximum Availability

#DR #DataGuard #Standby #PhysicalStandby #LogicalStandby #SnapshotStandby #Database #Exadata #RAC #ASM #Oracle

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-- zero data loss
-- redo transport synchronous (applying the transactions at the same time on the primary and secondary database servers)
-- It will allow the primary to continue and the standby to fall slightly behind

Maximum Performance
-- Minimal data loss
-- redo transport is done asynchronously

Maximum Protection
-- zero data loss
-- redo transport is synchronous (applying the transactions at the same time on the primary and secondary database servers)
-- Primary will waits for a response from standby
-- Primary will halt in case no acknoldgement from standby

5) Creating a Physical Standby Database
https://docs.oracle.com/en/database/oracle/oracle-database/19/sbydb/creating-oracle-data-guard-physical-standby.html#GUID-0FD317D6-1A49-4DB3-A141-D00CB3089E84

6) Creating a Logical Standby Database
https://docs.oracle.com/en/database/oracle/oracle-database/19/sbydb/creating-oracle-data-guard-logical-standby.html#GUID-3666CA35-D993-44B6-8D70-A2B8B9EC8B2E