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1.Is it manadatory to have it in archive log mode ?
Only if you switch the its role to Primary.
2.As it is in archive log mode , does it produce any archivelog ?
Thinking of the Primary and Standby database as one database is different roles.
In the "PRIMARY" role it must produce archive. Otherwise Data Guard cannot and would not work correctly if you do a switchover or failover.
SELECT DATABASE_ROLE FROM V$DATABASE;
Please consider closing you question if answered.
The Standby is a clone of the Primary. I assume we are talking Physical Standby.
Its does not produce archive in the Standby role. I have seen a Standby produce a log now and then, but not log after log like a primary. A Standby database does not write Redo or use Redo logs, it uses Standby Redo logs. Since Redo logs are not used, archive is not written.
Why does it need to produce archive in standby role?
Smart design I'm thinking. Why would Oracle make us add this complex step to a failover/switchover?
Why it is manadatory to enable archive log in standby?
Keep it simple if possible.
Data Guard Concepts and Administration 11g Release 2 (11.2) E10700-02
With all due respect this answer is very misleading. A Standby database does not produce archive logs. It receives redo data from a Primary database.
Your answer makes seem like the Standby is writing its own logs.
The Standby is not "producing archive logs", writing a copy of the Primary's archive and producing archive are two different things.
A Physical Standby will always create respectively get the same Archive Logs as the Primary.
They are used for Redo Apply - when Real-Time Apply can't (always) be done - there and they are mandatory.
A strategy to get rid of those (applied) Archive Logs is required, but you cannot (and don't want to) switch that off.
Technically speaking, the Standby really creates Archive Logs - when a Standby Log was filled up by the RFS, an ARCH process on the Standby creates an Archive Log.
Only when Archive Log Gap resolution takes place, an ARCH from the Primary will ship an Archive Log to the Standby.
A special case would be Logical Standby, where additionally to the above also Online Logs fill up and get archived.
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