Today log file contains
2021-03-10 11:01:58 EET checkpointer LOG: could not rename file
"pg_wal/000000010000000A0000003B": Permission denied
messages. Resource Manager shows that 000000010000000A0000003B is is
locked by process 30376
According to pg_stat_activity this is regular postgres process which is
in idle state and waiting for ClientRead event. It has executed last
query an hour ago.
It looks like wal files are not released after usage.
Andrus.