Oracle-L: RE: "direct path write" waits, please help

From: John Kanagaraj <john.kanagaraj_at_hds.com>
Date: Tue, 29 Jul 2003 09:44:28 -0800
Message-ID: <F001.005C7AD0.20030729094428@fatcity.com>

Hans,

Now let me guess.... Your disks are all RAID 5, right? And you possibly are bottlenecking on CPU as well? It is clear from the Top 5 that writes are an issue across the board, to TEMP (direct path write), Redo (log file sync) and DB files (db file parallel writes). Creating a RAID 1 set of disks and moving at least the TEMP, RBS, Redo (and Arch if present) to this will definitely help.

John Kanagaraj
Phone: 408-970-7002 (W)
Fax: 408 327 3086 (Call/Email prior to fax)

-----Original Message-----
Sent: Tuesday, July 29, 2003 8:54 AM
To: Multiple recipients of list ORACLE-L

Hi All,

Please help me tune this i/o related wait event. This is my 8.1.6 statspack top-5 wait list:
Top 5 Wait Events

~~~~~~~~~~~~~~~~~                                             Wait     % 
Total
Event                                               Waits  Time (cs)   Wt

Time

-------------------------------------------- ------------ ------------ 
-------
direct path write                                 304,867       35,925   
49.83
log file sync                                     145,015       23,441   
32.52
db file sequential read                            11,370        3,684    
5.11
file open                                             981        3,326    
4.61
db file parallel write                              1,893        3,115

4.32

You'll notice that 'direct path write' is the most expensive one in the list. I cannot find enough info on the net about this wait event, therefore I'm asking the real experts.

What events in Oracle trigger this wait event? In what way is this event different from "db file parallel write"? I mostly read comments that suggest lots of sorting and parallallel queries.

However, most sorts are done in memory and degree = 0 for all tables.

Any suggestions are very welcome.

Thanks,
Hans de Git

MSN Zoeken, voor duidelijke zoekresultaten! http://search.msn.nl

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Author: Hans de Git
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Author: John Kanagaraj
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