Number of standby logfiles on RAC Physical Standby Question/Clarification

So I've done a lot of physical standby database setups on single-instance dbs. Not so many on RAC however.

Oracle gives the following guidance for a RAC physical standby:

  (maximum # of logfiles +1) * maximum # of threads

The example given says:

  This example uses two online log files for each thread. Thus, the number of standby redo logs should be (2 + 1) * 2 = 6. That is, one more standby redo log file for each thread

On our RAC we have 6 nodes and I'm going to replicate to a 4 node standby RAC (though the DB only ever runs on 2 nodes of each)

So, on the primary I have :

24 Groups and 6 Threads. Each thread# has 4 Groups. The total # of logfiles is 24.

So Oracle's math here would be (24 + 1) * 6 or 150 standby logfiles.

That doesn't seem right to me.

Seems like it ought to be ((24 / 6) +1 ) * 6 for 30 standby logfiles

That would give 1 additional standby logfile per thread.

Is that correct?

Though I'm not sure what to do with the odd # threads *AND* the primary runs on thread# 5 & 6 while the standby will be on thread# 3 & 4 though maybe Oracle can automagically resolve/transmit the changes even though the thread #s might be different?

The doc for this (that I see repeated across multiple blogs) is https://www.oracle.com/technetwork/database/features/availability/maa-wp-10g-racprimaryracphysicalsta-131940.pdf (which is 10g but the advice should generally be true even if the math is incorrect)

Chris

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