Oracle Database / Data Guard & High Availability
ORA-16857: investigate a standby disconnected from its redo source
A disconnected destination warning can precede a large transport backlog. Establish how long the source has been unavailable and why.
Environment and inputs: Oracle Database 19c baseline · SQL*Plus-compatible SQL unless RMAN, DGMGRL, ADRCI or a host shell is specified. Check release, patch level, edition and container first.
Start with this diagnostic
Use the stated SQL, RMAN, DGMGRL or host shell and replace sample names with approved targets. DBA and V$ views need authorized catalog access in the correct container. Do not grant broad privileges for an example.
SELECT dest_id, status, error FROM v$archive_dest_status WHERE status <> 'INACTIVE';Read the result
On the sending database, destination state provides error context. The receiving member's logs and broker detail are needed for the full path.
Resolve and verify
Check network, listener, service and authentication in order guided by the error. Reestablish transport and confirm both connectivity and advancing redo.
Operational precautions
Do not remove the standby from monitoring or loosen protection settings as the initial response.