Re: confusion between max_standby_archive_delay, max_standby_archive_delay and max_standby_archive_delay

On 3/12/23 09:01, Laurenz Albe wrote:
> On Sun, 2023-03-12 at 01:53 +0530, Atul Kumar wrote:
>> Could someone help me in telling the difference between these three parameters
>> 1. max_standby_archive_delay
>> 2. max_standby_streaming_delay
>> 3. recovery_min_apply_delay
>>
>> My basic motive is to make the standby database server to be delayed to apply the
>> changes on itself,  if any data has been accidentally deleted/updated/ truncated
>> from the primary server.
>>
>> Which parameter do I need to configure to serve this purpose ? And
>> When will the remaining two parameters be used ?
>>
>> It would be great if anyone can explain them with a brief example.
> The parameter that does what you describe you want is "recovery_min_apply_delay".
>
> The other parameters only deal with delaying replication in the face of a
> replication conflict.
>
> Note that changes are immediately shipped to the standby, what is delayed with
> "recovery_min_apply_delay" is only the replay of the WAL information.
>
> So you can recover from a logical problem like DROP TABLE by stopping the
> standby, setting "recovery_target_time" to a time before the problem happened
> and then restarting the standby.  Then recovery will stop before the problem
> is replayed.

How do you determine what to set recovery_min_apply_delay to? 15 minutes... 
an hour... 8 hours... a week?  (OP's problem is better solved by restoring a 
recent backup to a separate instance, while letting replication do it's 
DR/HA things.)

-- 
Born in Arizona, moved to Babylonia.