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Switchover and failover are the two role-transition operations in Oracle Data Guard. Switchover is a planned, graceful transition (both databases remain available throughout). Failover is an emergency response to primary failure. Having a tested, documented playbook for both is a MAA operational requirement — discovering the procedure on the night of a failure is not a plan. Terminology Recap Term Trigger Data Loss? Primary State Afterward Switchover Planned maintenance None Becomes standby (online) Failover Primary failure Possible (ASYNC) or None (SYNC) Unavailable (failed) Reinstate After failover N/A Failed primary becomes new standby Always use the Data Guard Broker (DGMGRL) for role transitions. Direct SQL*Plus procedures are error-prone and lack the consistency checks the Broker provides. ...

Far Sync is an Oracle Data Guard feature that lets you achieve zero data loss (SYNC transport) to a remote standby database without paying the latency penalty on primary transactions. A Far Sync instance sits in a third location between the primary and the standby, receives redo synchronously from the primary (low-latency hop), and then ships it asynchronously to the standby (long-distance hop). 1. Reference Architecture 1.1 Environment Overview Role Hostname DB Unique Name Location OS Primary DB (RAC, 2 nodes) prim01.fra.example.com, prim02.fra.example.com ORCL_FRA Frankfurt DC (AZ-1) OL 8.9 Far Sync Instance farsync01.fra.example.com ORCL_FS Frankfurt DC (AZ-2) OL 8.9 Physical Standby (RAC, 2 nodes) stby01.ams.example.com, stby02.ams.example.com ORCL_AMS Amsterdam DC OL 8.9 DGMGRL / Observer host observer01.fra.example.com — Frankfurt DC (AZ-3) OL 8.9 Oracle version: 19c (19.23 RU) Primary ↔ Far Sync network: Dedicated 10 GbE VLAN, round-trip latency ≈ 0.4 ms Far Sync ↔ Standby network: WAN link, round-trip latency ≈ 8 ms DB_NAME: ORCL (same for all members); DB_UNIQUE_NAME differs per member 2. Live Redo Information Flow The diagram above shows the full geographical redo flow. Below is the step-by-step explanation of how zero data loss is achieved: ...