Re: V$FILESTAT reports very long average write times.

Don't worry about it. Oracle has problems working out a meaningful write time when using any form of async, or pseudo-async write process. This includes io-slaves,
multiple db_writers, and async I/O.

Quite often you find a rough relationship between the file number and the average
write time because of the way that Oracle batches up blocks for writing, and then
allocates the completion time for all batches in a cycle as the average time for every block.

-- 
Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk

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"J.W." <jwngaa_at_att.net> wrote in message
news:8rt0d0pg4erlgbd89d782qm16td8v2e57j_at_4ax.com...


> Does anyone have some clues as to why average write times are so high?

>

> I'm pretty certain the underlying disk i/o is ok.  I can consistently

> get 15mb/sec write times in UNIX outside of Oracle.  Since this is an

> IBM ESS F20, I was hoping to get 5 milliseconds or less average write

> times.  Another reason I don't believe basic disk i/o is a problem

> because the "temp" datafiles are written vey fast.  I believe TEMP

> tablespace files bypass SGA management so I think the write times of

> 100+ milleseconds has something to do with an incorrect setting in

> init.ora.

>

> The statspack report for "log file sync" and "db file parallel write"

> don't seem particularly high either.

>

> Any insights helpful.

>

> Excerpt of V$FILESTAT:

>

>

> FILE#    PHYBLKWRT        AVG NAME

> ----- ------------ ----------

> ----------------------------------------------

>     3      301,856       2.53 /oracle/PRD/sapdata10/temp_1/temp.data1

>    59      231,850       4.20 /oracle/PRD/sapdata9/temp_3/temp.data3

>   226      152,052     168.04 /oracle/PRD/sapdata10/undo_4/undo.data4

>   227      142,045     153.58 /oracle/PRD/sapdata10/undo_5/undo.data5

>   224      133,753     143.53 /oracle/PRD/sapdata10/undo_2/undo.data2

>    89      131,659       3.01 /oracle/PRD/sapdata9/temp_4/temp.data4

>   223      127,839     120.86 /oracle/PRD/sapdata10/undo_1/undo.data1

>   225      112,634     164.32 /oracle/PRD/sapdata10/undo_3/undo.data3