/epost1
-Original Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 20, 2001 7:56 AM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Small rollback segments can be recycled
without
http://www.geocities.com/epost1
-Original Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 20, 2001 7:56 AM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Small rollback segments can
To keep the rollback segments in buffer, so that rolling around the rollback
segments happens before blocks are written to disk. Which will increase
snapshot to old, but increase performance.
Do not criticize someone until you walked a mile in their shoes, that way
when you criticize them, you
the snapshot too old query mortality rate?
|
| -Original Message-
| From: Babette Turner-Underwood
[mailto:[EMAIL PROTECTED]]
| Sent: Monday, August 20, 2001 9:22 AM
| To: Multiple recipients of list ORACLE-L
| Subject: RE: Performance analysis (enqueue and buffer busy waits)
|
|
| I am
a
try.
Thanks,
Ethan
http://www.geocities.com/epost1
-Original Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 20, 2001 7:56 AM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Small
I am curious.
What are you trying to accomplish by
decreasing rollback segment size??
- Babette
-Original Message-
Lewis
Sent: Tuesday, August 14, 2001 6:52 PM
To: Multiple recipients of list ORACLE-L
Looking at your trace file, most of your lost time appears
to be in an update of
Small rollback segments can be recycled
without being written to disc. This can
reduce the total write-load on the system
and enhance your general use of the
db_block_buffer.
Jonathan Lewis
Host to The Co-Operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
Author of:
:56 AM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Small rollback segments can be recycled
without being written to disc. This can
reduce the total write-load on the system
and enhance your general use of the
db_block_buffer
no
improvements on anything during testing.
Thanks,
Ethan
-Original Message-
From: Post, Ethan [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 20, 2001 11:13 AM
To: Multiple recipients of list ORACLE-L
Subject: RE: Performance analysis (enqueue and buffer busy waits)
FYI, in a previous message I
Increase the snapshot too old query mortality rate?
-Original Message-
From: Babette Turner-Underwood [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 20, 2001 9:22 AM
To: Multiple recipients of list ORACLE-L
Subject: RE: Performance analysis (enqueue and buffer busy waits)
I am
Ignore (or at least treat very lightly) the comments about DBWm.
Excessive database writes can cause log file sync waits, as
dbwr calls lgwr to write the log protecting the blocks it is
about to write. In this case, you will see v$session_event
for the db writers showing log file waits.
unless the client wants to pay to have the job rewritten which is
going to be big $.
-Original Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, August 15, 2001 4:36 AM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy
Could you post the URL for the trace file
again.
One observation - 3,000 commits per
minute seems very odd for processing
230 sales order lines per minute.
Also 3,000 commits per minute doesn't
seem to be consistent with the trace file
which I can no longer see that had one
update executed
Enqueue waits cannot cause buffer busy waits,
but the absence of indexes (and you point out
missing FK indexes) can result in excessive
tablescanning, and tablescanning can result
in buffer busy waits.
Jonathan Lewis
Hi Jonathan,
thanks for answering.
there's something I'd like to know, hope
PROTECTED]
08/15/01 01:53 PM
Please respond to ORACLE-L
To:Multiple recipients of list ORACLE-L [EMAIL PROTECTED]
cc:
Subject:RE: Performance analysis (enqueue and buffer busy waits)
12 CPU machine redo logs on separate disks and controller, nothing else on
them
-Original Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, August 15, 2001 12:56 PM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Could you post the URL for the trace file
again.
One observation
Inserts do nothing special - there won't be pre-existing
child rows (and if there are, the insert is going to get
a duplicate in index error)
Updates that don't affect the key value do nothing special.
Updates that change the parent key value (and this
could even mean the old Forms 'update
]
cc:
Subject:RE: Performance analysis (enqueue and buffer busy
waits)
12 CPU machine redo logs on separate disks and controller, nothing else on
them. Application puts PK's on data tablespace so might be some contention
there, other indexes are on index
Hi list:
I've been analyzing an instance's performance for
some time. I found a lot of enqueue and a lot of
buffer busy waits.
Tracing the instance's sessions for some time I found
that enqueue waits are mostly because of FK not being
indexed. This of course generated shared locks (level
4)
Hi pablo,
try identifying the segments that are being contended
for using information of p1,p2 for buffer busy waits
and add more freelists for these segments. This
assumes that you have already separated your data and
indexes appropriately overe separate mount points.
As for enqueues leading
Enqueue waits cannot cause buffer busy waits,
but the absence of indexes (and you point out
missing FK indexes) can result in excessive
tablescanning, and tablescanning can result
in buffer busy waits.
Jonathan Lewis
Seminars on getting the best out of Oracle
Last few places available for Sept
Hi Deepak:
thanks for answering, I've already identified the
objects incurring into BBW but I also know that the p3
parameter for the BBW is 0 !! (this means that the
session A had to wait because the block that session A
needed, was being read from disk to Buffer Cache by
session B).
I
Message-
From: Jonathan Lewis [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, August 14, 2001 1:27 PM
To: Multiple recipients of list ORACLE-L
Subject: Re: Performance analysis (enqueue and buffer busy waits)
Enqueue waits cannot cause buffer busy waits,
but the absence of indexes (and you point out
of list ORACLE-L
|Subject: Re: Performance analysis (enqueue and buffer busy waits)
|
|
|
|Enqueue waits cannot cause buffer busy waits,
|but the absence of indexes (and you point out
|missing FK indexes) can result in excessive
|tablescanning, and tablescanning can result
|in buffer busy waits
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