Where to see whether Direct_i/o enabled

[engiri]

Enable Direct I/O for OCFS is a suggestion from one of a site, but I could not get the details how to enable it. where to see whether it is enabled.

This is for a performance analyssis where our
Test environment runs a sample query 10 times faster than live
environment with OCFS.
We have chosen a table with 8 million records.
Db sequential read is high.
Trace file is attached.
Thanks

[davey23uk]

have you tried tuning your queires first, db_file_sequential_read is mainly a wait on mis-use of indexes

but to see if it is used show parameter filesystemio_options

[engiri]

Thanks for your valuable response.
NAME_COL_PLUS_SHOW_PARAM TYPE VALUE_COL_PLUS_SHOW_PARAM
---------------------------------------------------------------- ----------- ----------------------------
filesystemio_options string none

The query is tuned. It is using the correct index (Rebuilt on request from metalink during our analysis yesterday)

[davey23uk]

ah index rebuilds, I hope they did proper analysis and determined why it needed to be rebuilt instead of just suggesting it randomly

You arent using direct i/o there are articles on Metalink on how to set it up, but I would still look at the query

[engiri]

Ya. For Itanium linux AS 2.1 , and ocfs 1.01 oracle Oracle told that they will analyse after analysing the strace, and statspacks.
We are going to enable the direct I/o. Any body have suggestions on enabling for the above environment. Thanks

[hrishy]

Hi Engiri

Mladen Googal answered my question sometime back.

On FC3, with another version, things look like this: 
gettimeofday({1115516619, 411653}, NULL) = 0 
gettimeofday({1115516619, 411723}, NULL) = 0 
pread(15, "\25\302\0\0\27\0\0\0\311\6\0\*0\377\377\1\4\255E\0\0\3\0"...*, 16384, 376832) = 16384 
gettimeofday({1115516619, 428299}, NULL) = 0 
stat64("/oradata/10g/oracle/sy*stem01.dbf", {st_mode=S_IFREG|0640, st_size=629153792, ...}) = 0 
open("/oradata/10g/oracle/syst*em01.dbf", O_RDONLY|O_DIRECT|O_LARGEFILE) = 18 
close(18)                               = 0 
open("/oradata/10g/oracle/syst*em01.dbf", O_RDWR|O_SYNC|O_DIRECT|O_LARGE*FILE) = 18 
fcntl64(18, F_SETFD, FD_CLOEXEC)        = 0 
io_submit(0xb74a4000, 0x1, 0xbfffe1b8)  = 1 
io_getevents(0xb74a4000, 0x1, 0x1, 0xbfffe5bc, 0xbfffe148) = 1 
fcntl64(18, F_GETFL)                    = 0xd002 (flags O_RDWR|O_SYNC|O_DIRECT|O_LARGE*FILE) 
fcntl64(18, F_SETLK64, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0}, 0xbfffe620) = 0 
gettimeofday({1115516619, 435080}, NULL) = 0 
pread(15, "\25\302\0\0\23\0\0\0\226\7\0\*0\377\377\1\4CS\0\0\0\310"..., 16384, 311296) = 16384 
gettimeofday({1115516619, 435487}, NULL) = 0 
gettimeofday({1115516619, 435549}, NULL) = 0 

You can easily see files being open with O_DIRECT flag. Unfortunately, 
this is not version 9: 


SQL*Plus: Release 10.1.0.4.0 - Production on Sat May 7 21:42:12 2005 


Copyright (c) 1982, 2005, Oracle.  All rights reserved. 


Connected to an idle instance. 


SQL> startup mount 
ORACLE instance started. 


Total System Global Area  201326592 bytes 
Fixed Size                   778452 bytes 
Variable Size              78651180 bytes 
Database Buffers          121634816 bytes 
Redo Buffers                 262144 bytes 
Database mounted. 
SQL> alter database open; 


Database altered. 


when the database was mounted, I attached strace to dbw, like this: 


$ ps -fu $LOGNAME|grep dbw 
oracle   10996     1  0 21:42 ?        00:00:00 ora_dbw0_10g 
oracle   11045 11021  0 21:43 pts/0    00:00:00 grep dbw 
$ strace -o /tmp/dbw.out -p 10996 
Process 10996 attached - interrupt to quit 


when that was done, I opened the database. The result is above. I don't 
know about whether direct I/O would work on RH ES 3.0, but that is how you 
can check. You have the same hammer called "strace". May the force be with 
you.

Additionally you can have a look at this thread
http://groups-beta.google.com/group/...1f5fbf2a417381

regards
Hrishy

[engiri]

Thanks . I found they are useful.
Regards