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Home -> Community -> Mailing Lists -> Oracle-L -> RE: RE: controlfile schema global enqueue lock
Steve,
Thank you so much for taking time to reply. I did run couple of times the
enque_lock script as you suggested. CF waiting is really minimum. I noticed
the maximum enqueue comes from MR which is Media Recovery in share lock.
Should I need to concern this or this is just a very normal symptoms for the
database nature?
The real exclusive lock comes from TX. Right now I am starting to look into
it.
MR-8-0 2 S 0 MR-80-0 2 S 335666 MR-81-0 2 S 335238 MR-82-0 2 S 334850 MR-83-0 2 S 334473 MR-84-0 2 S 334094 RESOURCE SID HOLDING WANTING SECONDS
-------------------- ---------- ------- ------- ----------
MR-85-0 2 S 333672 MR-86-0 2 S 333131 MR-87-0 2 S 332593 MR-88-0 2 S 331998 MR-89-0 2 S 331386 MR-9-0 2 S 0 MR-90-0 2 S 330764 RT-1-0 3 X 0 TM-2750-0 1459 SX 1262 406 SX 987 987 SX 968 RESOURCE SID HOLDING WANTING SECONDS
-------------------- ---------- ------- ------- ----------
TM-2750-0 1474 SX 957 462 SX 411 286 SX 336 TM-3196-0 1318 SX 0 TS-3-16866818 5 SX 332462 TX-1048594-158974 1208 X 1 TX-1048595-158908 1170 X 0 TX-1048640-159199 475 X 1 TX-1835008-159738 1474 X 957 TX-1835015-159892 1172 X 64
Thanks,
Joan
-----Original Message-----
Sent: Friday, February 02, 2001 5:40 AM
To: Multiple recipients of list ORACLE-L
Hi Joan,
This filtered into my Inbox folder because you mentioned my name. I've not
been
following the thread, but I'll comment on the output below.
Normally when seeing CF and ST enqueue waits and a lot of time spent in
'enqueue' waits I would suspect the ST enqueue to be the problem, rather
than
the CF enqueue. CF enqueue waits are seldom longer than half a second or so.
The
typical situation is one session doing a controlfile transaction and others
waiting to read the controlfile. It is relatively rare to need to make two
independent changes to the controlfile at the same time. By contrast, the ST
enqueue is held for many seconds when it is taken, and the waiters always
want
an exclusive lock too.
I suggest that you get a few samples of the enqueue waits using my
'enqueue_locks.sql' script. The new version reports the name of any
background
process involved rather than just its sid, which might be helpful here. You
may
also want to hack the script so that it only shows ST and CF enqueues. Then
run
it intermittently until you see something interesting. Then run it several
times
in quick succession to see what happens. If I'm right you see that the CF
waits
are relatively brief, whereas the ST lock contention will be relatively
enduring. If so, I'm sure you'll know what to do.
If it is the CF enqueue that is the source of most of the waits, then
knowing
which sessions are the holders and waiters will be a help in further
diagnosis
anyway.
@ Regards, @ Steve Adams @ http://www.ixora.com.au/ @ http://www.christianity.net.au/
-----Original Message-----
Sent: Friday, 2 February 2001 2:21
To: Multiple recipients of list ORACLE-L
Dick,
The system is not in archivelog mode. If the database crashed, I was told
they don't care at all. They just rebuilt a shell database and let getter
and feeder processes gradually feed the database. (The getter will check the
url in the database, if didn't find then will go to the origin server to get
the url) Of course, it will impact the performance. The end user at that
region will experienced the slow access. We just have 5 tables, spilt into
22 separate raw disks. No i/o problem at all. Now the problems is where is
control file enqueue come from? I thought since we have too many log switch
can cause the cf enqueue problem. But that is not true either. Right now we
don't have too many 4 per hr. still have the enqueue problem. We did'nt set
any slave parameter. Oh, we set parallel_max_servers to 5, all the tables
have 50 freelist and we have 8 getter and feeder processes running all the
time.
I run couple Steve Adams scripts,
SQL> @enqueue_stats.sql
TY GETS WAITS
-- ---------- ----------
CF 3272862 679426 CI 140 0 CU 4071 0 DL 29 0 DR 27 0 DV 83 0 HW 3646713 437 IS 22669 0 MR 158 0 PE 5337 0 PR 15 0 PS 65 0 RT 1 0 SQ 1902 0 ST 5763 4692 TM 12264283 0 TS 57 0 TT 28 0 TX 12099800 19 US 5781 0
SQL> @response_time_breakdown.sql
MAJOR MINOR WAIT_EVENT SECONDS
-------- ------------- ---------------------------------------- --------
CPU time parsing n/a 4920 reloads n/a 70 execution n/a 74532 disk I/O normal I/O db file sequential read 373254 full scans db file scattered read 2038 direct I/O direct path read 80465 direct path write 36378 other I/O control file parallel write 15312 control file sequential read 9082 db file parallel read 537 waits DBWn writes rdbms ipc reply 136 local write wait 1 LGWR writes log file switch completion 12681 enqueue locks enqueue 5716812 other locks latch free 82345 library cache pin 51513 buffer busy waits 27627 row cache lock 7403 library cache lock 15 buffer deadlock 1 index block split 0 latency commits log file sync 165491 network SQL*Net more data from client 101088 SQL*Net more data to client 1143 SQL*Net message to client 457 SQL*Net break/reset to client 287 file ops file open 37 process ctl process startup 1 misc refresh controlfile command 13197 reliable message 0
This database bounced yesterday. So the data should be refresh. We pined all the sys package into share pool.
Thanks,
Joan
-----Original Message-----
Sent: Thursday, February 01, 2001 10:59 AM
To: Joan Hsieh; Multiple recipients of list ORACLE-L
Joan,
HUMMMMMMM! Lots to think about here. For one, if your not doing any
backups
what is the plan for when a disk drive fails? Predicting that is similar to
predicting the next asteroid impact on the earth, it's not a matter of if,
but
when. After that drive gets replaced, something has to be put back down
there.
OH, your on a raid or mirrored system!! That's nice, same scenario, just
more
drives to worry about.
But we digress. First, is this system in archivelog mode? If your not
doing backups, why archive the redo information? Are each of these redo
files
on separate drives, or is that the hottest drive in the system? Might be a
good
idea to "spread the wealth". Is there only one control file or more than
one?
are they on the same drive? are they mixed up with DB files? is one or
more on
very busy drives? What is the setting of DBWR_IO_SLAVES and
DB_WRITER_PROCESSES?
I'd also have a discussion with the applications people. While I
understand
that stuff on the Internet is constantly changing, all of it is not changing
every hour. News stuff normally has a 24 hour life expectancy. What will
enhance the overall performance of your site would be a process that
accumulates
historical life expectancies for various types of content there by allowing
the
processes that refresh your url data to have some intelligence built into
them.
Dick Goulet
____________________Reply Separator____________________ Author: "Joan Hsieh" <Joan.Hsieh_at_mirror-image.com> Date: 2/1/2001 10:25 AM
Dick,
The database size is 200Gb (datafiles), not including the redolog. This is a internet content delivery company. The database structure is very simple. Some processes called getter continually insert the http site to the database. Other processes keep check the url is expired or not. Based on that, will do delete the url. So we do have a lot of insert, update (update the expire date) and delete. The interesting thing is we don't do backup. even not cold backup. No snapshot either. Since the content of internet is keeping change. There is no point to backup. The major thing is performance. We all use raw disk on sun 5.6 or HP. The db_block_size is 8k, db_block_buffer is 50000. The hit ratio is around 85%.
Joan
-----Original Message-----
Sent: Thursday, February 01, 2001 9:33 AM
To: Joan Hsieh; Multiple recipients of list ORACLE-L
Joan,
Something is indeed very fishy in London. The first question I would
ask is
what is creating so much redo generation? 9x250MB = 2.1GB of data changes
inside of that hour. One thought may be that the database is still in hot
backup mode from a previously disturbed backup. The other is that several
users
are doing a lot of temporary table creation, but not in the temp space.
What is the size of this database? Where does incoming data come
from?
Are their a lot of very frequently refreshed snapshots? Do they do a full
refresh vs a fast refresh? What is the db_block_buffer hit ratio like?
Having
a low hit ratio can indicate an excessively busy dbwr writing dirty blocks
to
disk which can cause lots of check points.
Dick Goulet
____________________Reply Separator____________________ Author: "Joan Hsieh" <Joan.Hsieh_at_mirror-image.com> Date: 2/1/2001 6:05 AM
Dear Listers,
Our database in London has tremendous cf enque lock. Since I am new here. I checked the parameter found the log_checkpoint_interval set to 3200 and log_checkpoint_timeout set to default (1800 sec). So I suggest to set log_checkpoint_interval to 100000000 and log_checkpoint_timeout to 0. The second thing I found we have average log switch is 6 t0 8 per hour. We have 40 redo logs, each of them is 250m. Our log buffer set to 1m. I believe after we changed the parameter, the control file schema global enqueue lock should be released. But it get worse, we have 98% control file enqueue lock now. I think we have too many log switch (9 per hour now)and suggested to increase the log to 500m, but our principle dba is not convinced, he think log buffer size should play a more important role.
Any ideas,
Joan
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Author: Joan Hsieh
INET: Joan.Hsieh_at_mirror-image.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
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Author: Steve Adams
INET: steve.adams_at_ixora.com.au
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
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Author: Joan Hsieh
INET: Joan.Hsieh_at_mirror-image.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Mon Feb 05 2001 - 11:23:10 CST
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