Hi Joan,
You don't have a problem unless there is a session WANTING a lock on the
resource. By "something interesting", I meant a session waiting for a lock on
either the CF or ST enqueues. Then you run it repeatedly to see how long the
problem persists. Because you are going to run it repeatedly, it would be good
to hack the script to exclude all other enqueue types. Also, I note that you are
not running the new version of this script that gives the names of the
background processes instead of their SIDs.
@ Regards,
@ Steve Adams
@ http://www.ixora.com.au/
@ http://www.christianity.net.au/
-----Original Message-----
Sent: Tuesday, 6 February 2001 1:11
To: Multiple recipients of list ORACLE-L
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" <[EMAIL PROTECTED]>
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" <[EMAIL PROTECTED]>
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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