Re: rollback questions

Vince Laurent wrote:
> I am trying to understand rollbacks, at least understanding how SAP
> uses them and to tune them. We have been getting more ORA-01555s
> since our database crossed the 100G size. Right now the rollbacks are
> set to the default install. Here are the stats from a program called
> orastat (plug:GREAT TOOL!):
>
> sapprd:oraprd 3> ./orastat -ra
> 2002/12/20-16:19:35 orastat | oraver=8.1.7 oraver3=8.1 sqlcmd=sp
> 2002/12/20-16:19:35 orastat | ORACLE_SID=PRD
> ORACLE_HOME=/oracle/PRD/817_64
> 2002/12/20-16:19:35 orastat | Version=2.33
> orastat | Rollback Segments Statistics
>
> RSSize : Current rollback segment size in bytes
> -column removed, all 10641408 bytes (10M)
>
> A Xn's : Number of current transactions using the rollback segment
> -column removed, all currently 0
>
> HWMSize : High Water Mark size in bytes
> Wraps : Cumulative # of times a X'n continues writing from one
> extents to another existing extent
> Avg Actv: Avg # of bytes in active extents in the rbs
> measured over time
>
> Name Extends Gets HWMSize Wraps Avg Actv Waits
> ------ ------- ------ ---------- ------ --------- ------
> PRS_0 7 130478 25550848 176 2345674 12
> PRS_1 6 124295 19161088 162 2210725 2
> PRS_2 4 123095 19161088 161 2232942 0
> PRS_3 1 125297 12771328 163 2136828 1
> PRS_4 12 153932 36200448 154 17202515 3
> PRS_5 28 150456 63889408 178 2647096 5
> PRS_6 31 144235 42590208 210 8988732 15
> PRS_7 4 127866 19161088 172 2810635 1
> PRS_8 65 143432 138436608 232 95312420 2
> PRS_9 4 129341 19161088 175 2206473 2
> PRS_10 12 127924 31940608 174 2222152 3
> PRS_11 0 121028 10641408 143 2130736 0
> PRS_12 0 121148 10641408 146 2147608 0
> PRS_13 62 142333 142696448 222 2131274 1
> PRS_14 42 141261 91578368 223 6116854 3
> PRS_15 5 130087 19161088 179 2132704 4
> PRS_16 48 137197 108617728 210 2602272 2
> PRS_17 120 166012 191684608 310 2893642 2
> PRS_18 17 128125 38330368 175 4018525 1
> PRS_19 20 131124 53239808 186 15698495 0
>
> Questions:
> If the rollbacks are 10M each, how can the high-watermark be higher?
> Since SAP doesn't seem to use all of them equally, should a few
> smaller but LARGER ones work better?
>
> Thanks!
> Vince

Hi Vince,
there are some sap-notes regarding to RBS: 7634, 3807, 60233 which may help to understand the problems!

Thomas Received on Sat Jan 04 2003 - 05:54:44 CST