SLOW RESPONSE FROM ASMCMD AND V$ASM% QUERIES

(Doc ID 567392.1)

Last updated on JUNE 24, 2009

Applies to:

Oracle Server - Enterprise Edition - Version: 10.2.0.3 to 10.2.0.3
HP-UX Itanium

Symptoms

Why ASMCMD commands or selects on V$ASM_DISKGROUP or V$ASM_DISK views, are much slower on HP Itanium versus HP-UX PA RISC?

SLOW
(HP Itanium):

Queries against V$ASM_DISKGROUP,     takes 00:00:06.61 seconds
Queries against V$ASM_DISK,                   takes 00:00:06.23 seconds.
FAST
(HP-UX PA RISC):

Queries against V$ASM_DISKGROUP,     takes 00:00:00.01 seconds
Queries against V$ASM_DISK,                   takes 00:00:00.01 seconds.

Regarding the storage used by these servers, both servers are attached to the same storage system. Therefore, all the characteristics/features are the same.

Changes

Found <> (WORKING INSIDE ASMCMD IS VERY SLOW), however seems not related since this case of bad performance is also observed when querying the v$asm* views. Also, the count from v$asm_files is far from been close to 10,000 (i.e., 394). As for count from
v$asm_alias, in this case is 668.

ASM_DISKSTRING is set equally for both platforms, and is already restricting the discovery path to avoid any further delays when querying the views.

Provided the solution to edit $ORACLE_HOME/bin/asmcmdcore script, and change all references from v$asm_disk or v$asm_diskgroup, to v$asm_disk_stat or v$asm_diskgroup_stat, to speed up these queries. However, this does not explain why the same 10203 code installed on one flavor of HP, will run slower than another flavor of HP.

Issue cannot be reproduced if using local disks (i.e., If one is to dismount the diskgroups from external storage and then create a new logical volume in an internal disk and create a diskgroup with this new
lv.)

Sar on an OS test of the devices on both platforms, show there is no issue reported at the OS layer. One can do a test by executing the command 'dd if=<device name to test> of=/dev/null bs=48' in each environment. Results from sar were:

Test                        blks/s    avserv(ms)
~~~~~~~~~~~~~~~~~~~~~~~~    ~~~~~~    ~~~~~~~~~~
PA-RISC                     162458    0.56
Itanium-external storage    204392    0.45
Itanium-local storage       252017    1.13


Note: blks/s meaning input/output processed blocks per second, and avserv
meaning average time to serve an input/output request. Observe the
Itanium server, in both tests, processes more blocks than PA-RISC, and
Itanium with external storage has the minimum average time to serve a
request.

Cause

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