Re: Archive Log Size

Jonathan,
I have to admit I was also not expecting both LGWR and ARCH and only came across that because you suggested looking for creator. I didn't put this standby together, so I'll do a bit of digging to see how it is constructed. One question though (and the reason I didn't head down this path earlier). If archive_lag_time=900 on all instances, what is the hypothesis where the standby impacts the archive log size?

Thanks again.
Henry

On Tue, Mar 9, 2021 at 4:43 AM Jonathan Lewis <jlewisoracle_at_gmail.com> wrote:

> Interesting that of the two archived copies one is created by ARCH and the
> other by LGWR.
> What do your log_archive_dest_1 and log_archive_dest_2 look like ?
> For completeness I guess it's also worth checking
>
> log_archive_dest_state_1 and log_archive_dest_state_2
> log_archive_max_processes
>
> log_archive_duplex_dest
> log_archive_format
> log_archive_local_first
>
> What sort of standby setup do you have?
>
> Regards
> Jonathan Lewis
>
>
>
>
>
> On Mon, 8 Mar 2021 at 19:39, Henry Poras <henry.poras_at_gmail.com> wrote:
>
>> Hi Jonathan,
>> Thanks for responding so quickly.
>>
>> As expected, we have 2 public threads and no private threads (RAC). The
>> sizes of log_buffer, Redo Size, Fixed Size, public thread size as
>> documented above are identical for all three nodes.
>>
>> Looking at v$instance, all nodes have been up for ~10 days (not identical
>> startup_time, but within a day) with status of OPEN.
>>
>> I can't find any clues in v$archived_log
>> primary:sys_at_ohcops1> l
>> 1 select * from (
>> 2 select dest_id, thread#, sequence#, creator, first_time from
>> v$archived_log
>> 3 order by first_time desc, thread# asc, dest_id asc
>> 4 )
>> 5* where rownum <=20
>> primary:sys_at_ohcops1> /
>>
>> DEST_ID THREAD# SEQUENCE# CREATOR FIRST_TIME
>> ---------- ---------- ---------- ------- -------------------
>> 1 2 1056302 ARCH 08-03-2021 20:34:11
>> 2 2 1056302 LGWR 08-03-2021 20:34:11
>> 1 1 1126141 ARCH 08-03-2021 20:34:06
>> 2 1 1126141 LGWR 08-03-2021 20:34:06
>> 1 3 1164895 ARCH 08-03-2021 20:33:47
>> 2 3 1164895 LGWR 08-03-2021 20:33:47
>> 1 3 1164894 ARCH 08-03-2021 20:32:26
>> 2 3 1164894 LGWR 08-03-2021 20:32:26
>> 1 2 1056301 ARCH 08-03-2021 20:32:20
>> 2 2 1056301 LGWR 08-03-2021 20:32:20
>> 1 1 1126140 ARCH 08-03-2021 20:32:15
>> 2 1 1126140 LGWR 08-03-2021 20:32:15
>> 1 3 1164893 ARCH 08-03-2021 20:30:50
>> 2 3 1164893 LGWR 08-03-2021 20:30:50
>> 1 2 1056300 ARCH 08-03-2021 20:30:29
>> 2 2 1056300 LGWR 08-03-2021 20:30:29
>> 1 1 1126139 ARCH 08-03-2021 20:30:09
>> 2 1 1126139 LGWR 08-03-2021 20:30:09
>> 1 3 1164892 ARCH 08-03-2021 20:29:32
>> 2 3 1164892 LGWR 08-03-2021 20:29:32
>>
>> 20 rows selected.
>>
>> I'll keep looking.
>>
>> Henry
>>
>>
>>
>>
>> On Sat, Mar 6, 2021 at 3:41 AM Jonathan Lewis <jlewisoracle_at_gmail.com>
>> wrote:
>>
>>>
>>> RAC doesn't use private redo - so with 32 CPUs we'd expect two public
>>> threads with (granule - fixed - overheads)/2 as the log buffer size.
>>> Is this happening on all three instances (redo threads)?
>>> If you report the "first_time" from v$archived_log can you see a pattern
>>> to the timing of the switch.
>>> Is there any clue in the "creator" from v$archived_log ?
>>>
>>>
>>>
>>> One possible explanation for this (assuming you've discounted all the
>>> usual suspects): Are all three instances active when this happens?
>>> I haven't checked recently but when an instance is down the active
>>> instances may be "kicking" it (KK lock) on a regular basis to do a log file
>>> switch so that all instances have archived log files with SCNs that are
>>> reasonably close to each other. Maybe there's a side effect (or timing
>>> issue, or bug) related to this that means the kicking is happening too
>>> frequently and you're not getting through a lot of redo before it happens.
>>>
>>>
>>> Regards
>>> Jonathan Lewis
>>>
>>>
>>>
>>> On Fri, 5 Mar 2021 at 20:39, Henry Poras <henry.poras_at_gmail.com> wrote:
>>>
>>>>
>>>> - I was just rereading this thread and ran into a slightly
>>>> different case I am just starting to dig into. My environment is 11.2.0.4
>>>> RAC (3 nodes).
>>>>
>>>> The rough breakdown:
>>>> Granule size: 256M
>>>> > select * from v$sga;
>>>>
>>>> NAME VALUE
>>>> -------------------- ----------
>>>> Fixed Size 2269072
>>>> Variable Size 3.9460E+10
>>>> Database Buffers 8.8584E+10
>>>> Redo Buffers 227807232
>>>> cpu_count: 32
>>>> log_buffer: 220798976
>>>> public threads: 2 public (no private) 105M each
>>>>
>>>> primary:sys_at_ohcops1> l
>>>> 1 select
>>>> 2 indx,
>>>> 3 total_bufs_kcrfa,
>>>> 4 strand_size_kcrfa,
>>>> 5 index_kcrf_pvt_strand,
>>>> 6 space_kcrf_pvt_strand
>>>> 7 from
>>>> 8* x$kcrfstrand
>>>> primary:sys_at_ohcops1> /
>>>>
>>>> INDX TOTAL_BUFS_KCRFA STRAND_SIZE_KCRFA INDEX_KCRF_PVT_STRAND
>>>> SPACE_KCRF_PVT_STRAND
>>>> ---------- ---------------- ----------------- ---------------------
>>>> ---------------------
>>>> 0 215624 110399488 0
>>>> 0
>>>> 1 215624 110399488 0
>>>> 0
>>>>
>>>> redo logs: 256M
>>>> archive logs: 40-43M
>>>>
>>>> So if each public thread takes 105M, I have ~~46M left over. Filling
>>>> one thread and switching, as discussed in Jonathan's article, should give
>>>> me archive logs of ~105 M. Instead, I am getting an archive log of ~ the
>>>> rump size in the redo (256-105-105=46M).
>>>>
>>>> I checked the obvious (not a manual log switch, not
>>>> archive_lag_target).
>>>> I'll chime in if I find something interesting. Also wondering if any
>>>> obvious things I'm missing off the top.
>>>>
>>>> Henry
>>>> ===================================================================
>>>>
>>>>

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