Hi Mikhail,
Yes, non-zero flags definitely trigger gathering of stale statistics regardless
of the number of modifications. For flags = 1 that’s a correct behavior, since
it’s a truncate. For flags=8 we still don’t know. I’m going to chase the
application people tomorrow to rerun the load jobs on the restored database. I
hope I’ll catch the culprit in the trace.
Best regards,
Nenad
From: Mikhail Velikikh <mvelikikh@xxxxxxxxx>
Sent: Montag, 8. März 2021 20:13
To: Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>
Cc: Jonathan Lewis <jlewisoracle@xxxxxxxxx>; ORACLE-L (oracle-l@xxxxxxxxxxxxx)
<oracle-l@xxxxxxxxxxxxx>; nigel.bayliss@xxxxxxxxxx; neil_chandler@xxxxxxxxxxx
Subject: Re: stale partition statistics
Hi Nenad,
I got the same flags after one database upgrade from 12.2 to 19.7. Basically,
there was a list partitioned table, and the gather stats job started collecting
statistics on the table's indexes everyday following the 19.7 upgrade (I
believe on the global ones).
While I was investigating the issue, I found that some of data dictionary views
were looking at that MON_MODS_V.FLAGS to determine the staleness - that is why
the statistics were regathered every day. The exact meaning of that flags value
is somewhere in DBMS_STATS or the packages calling from it - at least that is
where I found it then.
I checked my notes, and I tried several different things to get stats back to
normal, such as:
exec dbms_stats.delete_table_stats('owner', 'table_name', stat_category=>
'OBJECT_STATS,SYNOPSES')
exec dbms_stats.gather_table_stats('owner', 'table_name')
The statistics preferences were as follows:
SQL> SELECT
2 owner, table_name,
3
DBMS_STATS.get_prefs(ownname=>USER,tabname=>table_name,pname=>'INCREMENTAL')
incremental,
4
DBMS_STATS.get_prefs(ownname=>USER,tabname=>table_name,pname=>'GRANULARITY')
granularity,
5
DBMS_STATS.get_prefs(ownname=>USER,tabname=>table_name,pname=>'STALE_PERCENT')
stale_percent,
6
DBMS_STATS.get_prefs(ownname=>USER,tabname=>table_name,pname=>'ESTIMATE_PERCENT')
estimate_percent,
7 DBMS_STATS.get_prefs(ownname=>USER,tabname=>table_name,pname=>'CASCADE')
cascade,
8 DBMS_STATS.get_prefs(pname=>'METHOD_OPT') method_opt
9 FROM dba_tables
10 WHERE table_name ='table_name'
11 and owner='owner'
12 ORDER BY owner, table_name;
OWNER TABLE_NAME INCREMENTAL GRANULARITY
STALE_PERCENT ESTIMATE_PERCENT CASCADE
METHOD_OPT
---------- -------------------- -------------------- --------------------
-------------------- ------------------------------ -------------------------
-------------------------
owner table_name TRUE AUTO 10
DBMS_STATS.AUTO_SAMPLE_SIZE DBMS_STATS.AUTO_CASCADE FOR ALL
COLUMNS SIZE 1
There was also INCREMENTAL_STALENESS=USE_STALE_PERCENT set.
The way I checked the flags is using the query like this:
select * from sys.optstat_snapshot$ where obj#=185925 order by timestamp;
OBJ# INSERTS UPDATES DELETES FLAGS TIMESTAMP
---------- ---------- ---------- ---------- ----------
---------------------------------------------------------------------------
185925 165103 557906 0 0 11-MAY-20
10.18.43.791891 PM -04:00
185925 603978 558015 0 0 11-MAY-20
11.18.47.734575 PM -04:00
185925 673059 558524 0 0 12-MAY-20
01.03.54.386869 AM -04:00
185925 1294183 605041 0 0 12-MAY-20
02.03.58.300521 AM -04:00
185925 1358957 692646 0 40 12-MAY-20
02.35.52.733528 AM -04:00
185925 0 242425 0 0 12-MAY-20
03.34.04.838415 AM -04:00
185925 0 242425 0 40 12-MAY-20
03.59.42.940827 AM -04:00
185925 0 1 0 40 12-MAY-20
04.08.15.887380 AM -04:00
185925 0 0 0 40 12-MAY-20
04.15.45.580398 AM -04:00
185925 0 638 0 40 12-MAY-20
04.25.43.490814 AM -04:00
185925 0 278 0 40 12-MAY-20
04.35.57.022339 AM -04:00
185925 0 8581 0 40 12-MAY-20
04.45.40.478107 AM -04:00
185925 0 85532 0 40 12-MAY-20
04.55.37.699201 AM -04:00
185925 89737 0 0 0 17-MAY-20
10.32.00.757830 PM -04:00
185925 175288 13533 0 0 17-MAY-20
11.32.05.038541 PM -04:00
185925 175288 13533 0 0 18-MAY-20
12.32.08.422136 AM -04:00
185925 175288 13533 0 0 18-MAY-20
01.32.12.059589 AM -04:00
185925 175288 13533 0 40 18-MAY-20
02.32.01.836936 AM -04:00
185925 0 0 0 40 18-MAY-20
03.33.57.325283 AM -04:00
185925 12005 0 0 0 18-MAY-20
08.44.27.382584 AM -04:00
185925 12005 941 0 0 18-MAY-20
09.44.29.421376 AM -04:00
185925 12005 4159 0 0 18-MAY-20
10.44.32.184351 AM -04:00
185925 12005 5365 0 0 18-MAY-20
11.44.33.433158 AM -04:00
185925 12005 5365 0 0 18-MAY-20
12.44.34.162253 PM -04:00
185925 12005 5365 0 0 18-MAY-20
01.44.35.163062 PM -04:00
185925 12005 5365 0 0 18-MAY-20
02.44.36.352044 PM -04:00
185925 12005 5365 0 0 18-MAY-20
03.44.37.308166 PM -04:00
185925 12005 5365 0 0 18-MAY-20
04.44.38.309023 PM -04:00
185925 12005 5365 0 0 18-MAY-20
05.44.39.285316 PM -04:00
185925 12005 5365 0 0 18-MAY-20
06.44.40.241425 PM -04:00
185925 12005 5365 0 0 18-MAY-20
07.44.41.296872 PM -04:00
185925 12005 5365 0 0 18-MAY-20
08.44.42.524968 PM -04:00
185925 12005 5365 0 0 18-MAY-20
09.44.43.561849 PM -04:00
185925 12005 5365 0 0 18-MAY-20
10.44.44.638588 PM -04:00
185925 12005 5365 0 0 18-MAY-20
11.44.48.566198 PM -04:00
185925 12005 5365 0 0 19-MAY-20
12.44.49.587112 AM -04:00
185925 12005 5365 0 0 19-MAY-20
01.44.50.610348 AM -04:00
185925 12005 5365 0 8 19-MAY-20
03.29.52.937021 AM -04:00
185925 12005 5365 0 8 19-MAY-20
04.29.54.274754 AM -04:00
..skip...
185925 39055 55056337 0 8 22-MAY-20
01.52.22.127686 PM -04:00
185925 39055 55056337 0 8 22-MAY-20
02.52.23.180742 PM -04:00
185925 39055 55056337 0 8 22-MAY-20
03.52.24.267023 PM -04:00
185925 39055 55056337 0 40 22-MAY-20
04.24.02.507669 PM -04:00
185925 0 0 0 8 23-MAY-20
04.37.38.529168 AM -04:00
I think I hit that issue in multiple environments. The flags was set to 8
following the upgrade and then I could not get rid of it. Raised an SR with
Oracle, but it went nowhere. The flags switching from 8 to 40 and backwards
might be due to the statistics gathering - cannot recall.
____________________________________________________
Please consider the environment before printing this e-mail.
Bitte denken Sie an die Umwelt, bevor Sie dieses E-Mail drucken.
Important Notice
This message is intended only for the individual named. It may contain
confidential or privileged information. If you are not the named addressee you
should in particular not disseminate, distribute, modify or copy this e-mail.
Please notify the sender immediately by e-mail, if you have received this
message by mistake and delete it from your system.
Without prejudice to any contractual agreements between you and us which shall
prevail in any case, we take it as your authorization to correspond with you by
e-mail if you send us messages by e-mail. However, we reserve the right not to
execute orders and instructions transmitted by e-mail at any time and without
further explanation.
E-mail transmission may not be secure or error-free as information could be
intercepted, corrupted, lost, destroyed, arrive late or incomplete. Also
processing of incoming e-mails cannot be guaranteed. All liability of Vontobel
Holding Ltd. and any of its affiliates (hereinafter collectively referred to as
"Vontobel Group") for any damages resulting from e-mail use is excluded. You
are advised that urgent and time sensitive messages should not be sent by
e-mail and if verification is required please request a printed version.
Please note that all e-mail communications to and from the Vontobel Group are
subject to electronic storage and review by Vontobel Group. Unless stated to
the contrary and without prejudice to any contractual agreements between you
and Vontobel Group which shall prevail in any case, e-mail-communication is for
informational purposes only and is not intended as an offer or solicitation for
the purchase or sale of any financial instrument or as an official confirmation
of any transaction.
The legal basis for the processing of your personal data is the legitimate
interest to develop a commercial relationship with you, as well as your consent
to forward you commercial communications. You can exercise, at any time and
under the terms established under current regulation, your rights. If you
prefer not to receive any further communications, please contact your client
relationship manager if you are a client of Vontobel Group or notify the
sender. Please note for an exact reference to the affected group entity the
corporate e-mail signature. For further information about data privacy at
Vontobel Group please consult www.vontobel.com <https://www.vontobel.com>.