Re: Number of standby logfiles on RAC Physical Standby Question/Clarification

Chris,

By "maximum # of logfiles", they mean the highest logfile count of all threads, which in your case is 4. So, the formula would be (4 + 1) * 6. The standby recovery threads will match the primary threads, regardless of how many nodes are on the standby.

Seth

On Wed, Mar 3, 2021 at 9:48 AM Seth Miller <sethmiller.sm_at_gmail.com> wrote:

> Chris,
>
> By "maximum # of logfiles", they mean the highest logfile count of all
> threads, which in your case is 4. So, the formula would be (4 + 1) * 6. The
> standby will recovery threads will match the primary threads, regardless of
> how many nodes are on the standby.
>
> Seth
>
> On Wed, Mar 3, 2021 at 9:47 AM Chris Taylor <
> christopherdtaylor1994_at_gmail.com> wrote:
>
>> Yeah I found another Oracle doc (also 10g) but in HTML format and it says:
>>
>> (maximum number of logfiles for each thread + 1) * maximum number of
>> threads
>>
>>
>> So , that seems to be more correct.
>>
>> I'm still a bit curious how the RAC will handle the thread differences
>> when replicating but I guess we'll find out.
>>
>>
>> On Wed, Mar 3, 2021 at 10:44 AM Andrew Kerber <andrew.kerber_at_gmail.com>
>> wrote:
>>
>>> I think the 30 number is correct, that is how I have always done it.
>>>
>>> On Wed, Mar 3, 2021 at 9:36 AM Chris Taylor <
>>> christopherdtaylor1994_at_gmail.com> wrote:
>>>
>>>> List,
>>>>
>>>> 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
>>>>
>>>>
>>>>
>>>
>>> --
>>> Andrew W. Kerber
>>>
>>> 'If at first you dont succeed, dont take up skydiving.'
>>>
>>

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