Read replica failover

Question

While trying to perform switchover between cross region read replica and primary instance of rds oracle I am getting error - “An internal error has occurred. Please try your query again at a later time” ?

Tushar Rajput · Accepted Answer

The most common cause of this error is the option group (on the primary or read replica) being in an invalid state.

Steps to Resolve - 
* **Check the option group status.** Verify the status of the option group associated with your DB instance. If the status shows as invalid, proceed to the next step.

* **Identify the incorrectly installed option.** Run the following query to determine which option failed to install correctly. Any option that exists in the option group but does not appear in the query output is the problematic one:

SELECT option_name, major_engine_version, port, lifecycle, change_state, install_start_time, install_end_time
FROM RDSADMIN.RDS_OPTION_INFO;

* **Assess downtime impact.** Before making changes, confirm whether removing and re-adding the identified option will cause downtime.

* **Remove and re-add the option**. Once you've confirmed the impact, remove the problematic option from the option group and add it back. If re-adding the option causes option group state to be invalid please fix this before moving forward. Verify that the option group returns to an in-sync state before attempting the switchover.

Taka · Answer

Before initiating switchover, validate the result of switchover_status from v$database -- it must be "TO PRIMARY" or "SESSIONS ACTIVE".
Run this on the replica instance:

```
SELECT SWITCHOVER_STATUS FROM V$DATABASE;
```
If the result is anything other than "TO PRIMARY" or "SESSIONS ACTIVE" (e.g. "NOT ALLOWED", "FAILED DESTINATION"), the switchover will be rejected by Oracle Data Guard internally, which surfaces as this generic error.

Read replica failover

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