There is an issue in a topology of 3 hosts.
Primary has a scheduled OS-task (every hour) to delete archive logs older 3 hours with RMAN. Archivelog deletion policy is configured to "Applied on all standby".
There are 2 remote log_archive_dest entries - Physical Standby and Downstream. Every day there appears a "RMAN-08120: WARNING: archived log not deleted, not yet applied by standby" in the task's logs and than it resolves in 2-3 hours.
I've checked V$ARCHIVE_LOG during the issue and figured out, that the redos are not applied on the Downstream server. I have not caught the issue on the Downstream server yet, but during the "good" periods all the apply processes are enabled, but the dba_apply_progress view tells me, that apply_time of the messages is 01-JAN-1970.
The dba_capture view tells that capture processes' statuses are ENABLED, status_change_time is approximately the time of the RMAN-issue resolved.
I'm new to the Golden Gate, Streams and Downstream technologies. I've read the reference Oracle Docs, but couldn't find anything about some schedule for capture or apply processes.
Could someone please help to figure out, what else to check or what to read? Grateful for every response. Thanks.