Question: What is the purpose of
the log_archive_dest_2 parameter? Why is it
recommended to have the value for log_archive_dest_2=/u01/app/oracle/dest/redo
VALID=FOR(ONLINE_LOGS,PRIMARY_ROLE)?
Answer: Oracle Data Guard
introduced the log_archive_dest_2 parameter to
specify to redo log type and database role, in a set of
matched pairs:
LOG_ARCHIVE_DEST_2 = file_directory_name, VALID
FOR=(redo_type, role)
where redo_type equals:
all_logfiles: When archiving redo log
files
online_logfile: When archiving
redo logs (physical standby)
standby_logfile: When
archiving standby redo log files.
and role equals:
all_roles: This is valid when the
database is in either primary mode or standby mode
primary_role: This is valid only
for the current primary database
standby_role: This is valid only
for the database running in standby mode
However, even through the default for
log_archive_log_dest_2 = (all_logfiles, all_roles), this
does not mean that this setting is correct for your database
configuration.
If we examine the differences between a logical standby
and physical standby database we know that the logical
standby ships redo directly and generates it's own redo log,
just as the primary database.
Also see
data guard transport copy redo log tips.
