RE: Who Write Undo Information From The DbCache To The Physically UndoDatafile.

Hi Sheldon

>I Would Like To Know , If Undo Block Is Brought In The Buffer Cache,
>During An Update.. SO What Process Write The Undo Block [Old Image] To
>The Physically Undo Datafile.

Just an observation...

Which processes opened the datafile of an undo tablespace?

linux:oracle:A920 /u00/app/oracle> lsof /u00/oradata/A920/undotbs01.dbf COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME oracle 18808 oracle 16uW REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18810 oracle 17u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18812 oracle 16u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18814 oracle 13u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18820 oracle 14u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18837 oracle 16u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18839 oracle 16u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 18841 oracle 16u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 29676 oracle 15u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

oracle 30232 oracle 14u REG 8,17 220209152 327696 =
/u00/oradata/A920/undotbs01.dbf

Ok, there are 10 processes... but if you carefully give a look to the = output only one has a write lock on it (flag "W"), i.e. 18808.

linux:oracle:A920 /u00/app/oracle> ps -fp 18808

UID        PID  PPID  C STIME TTY          TIME CMD
oracle   18808     1  0 May11 ?        00:00:08 ora_dbw0_A920

HTH
Chris

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