RE: Rollbacks - ORA-1555

From: Christine Turner <christine.turner_at_ips-sendero.com>
Date: Wed, 05 Dec 2001 08:59:38 -0800
Message-ID: <F001.003D5DE3.20011205084018@fatcity.com>

Hello All,

I changed the rollback segments, and here are the results. I'm now at 20 segments, 1 meg each, minextents 20, optimal 20. Here are the results after running the process within the application with auto-commits turned off...

data requests

2969079

CLASS                  COUNT
------------------ ---------
system undo header         0
system undo block          0
undo header                1
undo block                 0


 USN NAME       AVEACTIVE   OPTSIZE WAITS WRAPS EXTENDS   SHRINKS AVESHRINK
---- ---------- --------- --------- ----- ----- ------- --------- ---------
   0 SYSTEM             0               0     0       0         0         0
   2 SV_ROLL0      106086  20971520     0     1       0         0         0
   3 SV_ROLL1      106086  20971520     0     1       0         0         0
   4 SV_ROLL2      106086  20971520     0     1       0         0         0
   5 SV_ROLL3      106086  20971520     0     1       0         0         0
   6 SV_ROLL4           0  20971520     0     0       0         0         0
   7 SV_ROLL5      106086  20971520     0     1       0         0         0
   8 SV_ROLL6      106086  20971520     0     1       0         0         0
   9 SV_ROLL7      106086  20971520     0     1       0         0         0
  10 SV_ROLL8      106086  20971520     0     1       0         0         0
  11 SV_ROLL9      106086  20971520     0     1       0         0         0
  12 SV_ROLL10     201973  20971520     1     2       0         0         0
  13 SV_ROLL11          0  20971520     0     0       0         0         0
  14 SV_ROLL12     106086  20971520     0     1       0         0         0
  15 SV_ROLL13     106086  20971520     0     1       0         0         0
  16 SV_ROLL14     106086  20971520     0     1       0         0         0
  17 SV_ROLL15     106086  20971520     0     1       0         0         0
  18 SV_ROLL16     201973  20971520     0     2       0         0         0
  19 SV_ROLL17     106086  20971520     0     1       0         0         0
  20 SV_ROLL18     106086  20971520     0     1       0         0         0
  21 SV_ROLL19     106086  20971520     0     1       0         0         0

21 rows selected.

TSPACE TOTAL USED FREE --------------- --------- --------- --------- SV_ROLL_TSP 800 407 394 This doesn't look real good to me....am I correct??? I will try processing without the optimal being set to see what happens, while I await other response.

thanks!
Christine

-----Original Message-----
Thapliyal
Sent: Tuesday, December 04, 2001 5:12 PM To: Multiple recipients of list ORACLE-L

Hi Christine,

Your rollback segments look large to me based on the description you have given for your application. One way of eliminating header waits is to increase the number of rbs .. try this and post if this helps your stats..

Create total of 20 rollback segments
Specification for each rbs is : initial 1M next 1M minextents 20 maxextents unlimited optimal 20M

meaning that each rbs will have 20 extents initially and size of each rbs will be 20M initially. since you have 20 such rbs, total rbs used is 20 * 20M = 400M

if you observe, the above structure uses smaller sized large number of rollback segments as from your description below, it looks like you have a oltp system with large number of transactions

tell me if this helps ..

Deepak

Christine Turner <christine.turner_at_ips-sendero.com> wrote:
> RE: BMC Patrol DBXray / CA UnicenterGreetings
> All....
>
> I am some what new to the list, so forgive me if I
> don't have the proper
> etiquette in addressing my issue. I have a database,
> 8.1.6, running on
> Windows NT, that currently has 5 rollback segments.
> The specs are as follows
> for each segment:
>
> OPTIMAL 350M
> minextents 7
> maxextents unlimited
> initial 50M
> next 50M
>
> These segments are currently in one tablespace, for
> rollbacks only, which is
> sized at 2.5 gig, and currently the segments are
> taking 1.7 gig, obviously
> aprox 750 meg free.
>
> I have an application, written by our developers
> here, which is doing a
> functionality called "pricing". Within this process
> is alot of DML (updates
> and deletes) with some DDL inter-mixed. There is an
> auto-commit feature,
> which is currently commiting every 1000 records.
> There is also a locking
> feature, before the actual "fetches" the application
> is performing for it's
> cursors, and the developers are currently using
> "select * from table for
> update nowait" to lock the whole table for this
> process. The locking is in
> place because this particular process can use up to
> 5 different sessions.
>
> Currently the stats of the rollbacks look like this:
>
> data requests
> -------------
> 3817488
> >
> CLASS COUNT
> ------------------ ----------
> system undo header 0
> system undo block 0
> undo header 3
> undo block 1
> >
> USN NAME AVEACTIVE OPTSIZE WAITS WRAPS
> EXTENDS SHRINKS
> AVESHRINK
> ---- ---------- ---------- ---------- ----- -----
> ------- ---------- -------
> ---
> 0 SYSTEM 0 0 0
> 0 0
> 0
> 2 SV_ROLL0 0 367001600 2 0
> 0 0
> 0
> 3 SV_ROLL1 0 367001600 0 0
> 0 0
> 0
> 4 SV_ROLL2 0 367001600 1 0
> 0 0
> 0
> 5 SV_ROLL3 0 367001600 0 0
> 0 0
> 0
> 6 SV_ROLL4 0 367001600 0 0
> 0 0
> 0
>
> 6 rows selected.
> >
> TSPACE TOTAL USED FREE
> --------------- ---------- ---------- ----------
> SV_ROLL_TSP 2500 1751 750
>
> At times I have seen the "aveactive" column have
> some numeric value in it,
> but when the database and services are shutdown and
> brought back up, this
> number clears out.
>
> My question is this: how much larger are these
> rollbacks supposed to be
> before I can eliminate the waits and wraps? More
> importantly, eliminate the
> undo headers and block. I have done alot of testing,
> with different sizing,
> and I feel like I'm chasing my tail. This is a major
> feature of our
> software, so it's not like it can be "ran at night"
> to differ to a timing
> issue. I have also noticed, that PMON doesn't really
> "shrink" appropriately,
> not back to a state like they are when they are
> first created. At this
> point, I guess I'm looking for some insight, advice
> as to what to
> specifically do to tune these segments a little
> more.
>
> Thanks So Much, in advance....
>
> Christine
>

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Author: Deepak Thapliyal
  INET: deepakthapliyal_at_yahoo.com

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Author:  Christine Turner
  INET: christine.turner_at_ips-sendero.com

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Received on Wed Dec 05 2001 - 10:59:38 CST