Re: Archive Log Size

Jonathan,
According to the docs, "A 0 value disables the time-based thread advance feature" so I am going under the assumption that 900 means 900. Of course, sometimes docs lie.

Tim, what you suggest makes sense, but it doesn't match up with what I am seeing in this environment. There is some data in the first few entries in this thread. I can summarize over a larger time frame if you like. Basically, each thread is switching every couple of minutes or less, and the archive logs are consistently 40-43M (redo logs are 256M).

Henry

On Tue, Mar 9, 2021 at 4:14 PM Tim Gorman <tim.evdbt_at_gmail.com> wrote:

> Is it possible that, when archived redo log files are small, their
> modification time is 15 mins (i.e. 900 seconds) after the previous redo log
> file was created/archived?
>
> I might be missing the point of your original question, but if you're
> asking about archived redo log files being smaller than the online redo log
> files, then ARCHIVE_LAG_TARGET > 0 on a frequently-idle instance would
> explain that?
>
>
>
> On 3/9/2021 11:39 AM, Henry Poras wrote:
>
> archive_lag_target is 900
>
> On Tue, Mar 9, 2021 at 2:33 PM Tim Gorman <tim.evdbt_at_gmail.com> wrote:
>
>> What is the value of ARCHIVE_LAG_TARGET?
>>
>>
>> On 3/9/2021 11:29 AM, Henry Poras wrote:
>>
>> Basically that is it. Redo logs are 256M, archive logs are ~40M. There
>> was a similar issue/thread in this list ~6 weeks ago, but the solution to
>> that system doesn't fit with this case. Hope that helps.
>>
>> Henry
>>
>>
>> On Tue, Mar 9, 2021 at 2:23 PM Chris Taylor <
>> christopherdtaylor1994_at_gmail.com> wrote:
>>
>>> So what is the issue here exactly? I''ve read through this thread a few
>>> times without clearly understanding the "problem" .
>>>
>>> It seems like you're wondering about why the archivelogs are smaller
>>> than the redo logs maybe? But I'm not sure if that is the issue or not.
>>>
>>> Chris
>>>
>>>
>>> On Tue, Mar 9, 2021 at 1:51 PM Henry Poras <henry.poras_at_gmail.com>
>>> wrote:
>>>
>>>> I wonder if there is any way to see if the problem is local or from the
>>>> standby without temporarily disabling the standby. It would be nice to be
>>>> able to eliminate one of those two causes.
>>>>
>>>> Henry
>>>>
>>>> On Tue, Mar 9, 2021 at 12:54 PM Henry Poras <henry.poras_at_gmail.com>
>>>> wrote:
>>>>
>>>>> I liked that idea. Unfortunately,
>>>>>
>>>>> *physical standby*:sys_at_ohcopp2> select distinct bytes from v$log;
>>>>>
>>>>>
>>>>>
>>>>> BYTES
>>>>>
>>>>> ----------
>>>>>
>>>>> 268435456
>>>>>
>>>>>
>>>>>
>>>>> 1 row selected.
>>>>>
>>>>> *physical standby*:sys_at_ohcopp2> select distinct bytes from
>>>>> v$standby_log;
>>>>>
>>>>>
>>>>>
>>>>> BYTES
>>>>>
>>>>> ----------
>>>>>
>>>>> 268435456
>>>>>
>>>>>
>>>>>
>>>>> 1 row selected.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> *primary*:sys_at_ohcops1> select distinct bytes from v$log;
>>>>>
>>>>>
>>>>>
>>>>> BYTES
>>>>>
>>>>> ----------
>>>>>
>>>>> 268435456
>>>>>
>>>>>
>>>>>
>>>>> 1 row selected.
>>>>>
>>>>>
>>>>>
>>>>> On Tue, Mar 9, 2021 at 12:02 PM Jonathan Lewis <jlewisoracle_at_gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> That explains the LGWR/ARCH oddity.
>>>>>>
>>>>>> Next, let me display my ignorance: is it possible to configure your
>>>>>> standby with standby log files that are SMALLER than the primary log files
>>>>>> - I think it used to be necessary to have them matching in size, but maybe
>>>>>> that's changed since the good old days (of 10g). If a standby can survive
>>>>>> with standby log file smaller than primary log files then maybe your 40 -
>>>>>> 45MB is being dictated by the size of your standby log files.
>>>>>>
>>>>>> Regards
>>>>>> Jonathan Lewis
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, 9 Mar 2021 at 16:35, Henry Poras <henry.poras_at_gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Current parameter settings (same on all nodes) are:
>>>>>>>
>>>>>>> log_archive_dest_1
>>>>>>> LOCATION=USE_DB_RECOVERY_FILE_DEST VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
>>>>>>> DB_UNIQUE_NAME=xxxx
>>>>>>>
>>>>>>> log_archive_dest_2 SERVICE=xxxx LGWR ASYNC
>>>>>>> VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=xxxx
>>>>>>>
>>>>>>> log_archive_dest_state_1 enable
>>>>>>>
>>>>>>> log_archive_dest_state_2 ENABLE
>>>>>>>
>>>>>>> log_archive_max_processes 4
>>>>>>>
>>>>>>> log_archive_duplex_dest
>>>>>>>
>>>>>>> log_archive_format ARC%S_%R.%T
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> So log_archive_dest_2 has the deprecated LGWR parameter. It's
>>>>>>> dest_1, using FRA which is using ARCH. Huh?
>>>>>>>
>>>>>>> Henry
>>>>>>>
>>>>>>> On Tue, Mar 9, 2021 at 8:45 AM Henry Poras <henry.poras_at_gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> 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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