CPU performance


 
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Operating Systems AIX CPU performance
# 15  
Old 01-12-2017
Thanks zazzon and bakunin. The performance needs to be increased. As per the current outputs we can see that system is not streched but still memory is utilized. Currently the load is a serial load when tried to increase the load parallaly the system still takes the same time to complete, which we thought parallel should reduce the time.
And I need to check with the dba for cio or dio. I will revert soon.

Thanks again...
# 16  
Old 01-12-2017
CIO also includes the benefits DIO - afaik with jfs2 you usually use CIO anyway, no DIO.

If I recall it correct, it is just mounting the relevant filesystems with the cio option and have the setting in the init.ora that agent.kgb described. Though take care that not all Oracle FS maybe used with CIO!

Taken from: Managing Oracle disk I/O in AIX
Quote:
The IBM documentation ?Configuring IBM System Storage DS4000 Series For Oracle Database Applications? (October 2015) notes special considerations for AIX blocksizes:


?When CIO is used, the POSIX standard filesystem level I/O serialization mechanisms are disabled, which avoids inode contention issues.

If planning to use JFS2 CIO, be sure to isolate online redo logs and control files in a separate file system that was created with agblksize=512.

File systems which contain Oracle data (.dbf) files should be created with agblksize=4096 if db_block_size >= 4K or agblksize=2048 if db_block_size=2K.

On CIO-mounted filesystems that contain datafiles, the database block size needs to be multiple of agblksize.

This is not something that customers need to worry about except if the database block size is 2KB, in which case you need to make sure agblksize is 2KB, 1KB or 512 bytes.?

As mentioned by the other guys, you might have a check applicationwise, maybe some queries cost a lot of resources, that an index is not optimal or table scans are done etc.

Check this one, page 3:
IBM Systems Mag: In tune with Oracle
# 17  
Old 01-12-2017
Sorry for not replying earlier, starting a new project kept me busy the lst few days.

There are a few things that don't quite add up IMHO:

First, the initial vmstat-output says ~200GB memory, but the avm column only shows ~21 mio of pages, which is ~80GB. Where is the difference? Please post the output of lsattr -El mem0 to verify how much (real) memory you really have.

Second, you said you have 15 cores configured, but the vmstat output shows 16. I presume that was just a typo on your part, but please confirm.

Third, further posted outputs of ps suggest that you have different DB instances running (fininddb and finabrodb). How many database instances are running simultaneously?

Fourth, i don't understand why there are so many archiver processes shown in the ps-outputs. What exactly is/are the DB(s) doing (in terms of how many requests and of which size typically) and how many logs (of which size) are typically produced per time unit? Are there any dumps being taken, exports running or the like?

In light of further information i am of the same opinion as Scrutinizer: your are perhaps a victim of double caching. The high number of pending I/Os and fs I/O blocked with no pbuf are further indicative of this assumption. If (see above, this is why this information is important) you have only one DB instance and you have 80GB of RAM and nothing else running on the system increase the SGA to ~60-70GB and see how that works. If you have set FILESYSTEMIO_OPTIONS=SETALL as suggested by agent.kgb Oracle should open its DB files with concurrent I/O even if the filesystem is not mounted with the CIO option. Concurrent I/O bypasses the OS caching of FS operations but i presume you haven't activated that yet otherwise the picture of two different caching systems blocking each other should not be seen even if the SGA is too small (as it probably is right now).

Finally, a suggestion: when you use vmstat on concurrent systems use the "-w" option. This way you get a neat table as output and it is easier to assess the picture.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
# 18  
Old 01-16-2017
The db server is of 16 cores that was a typo mistake. Its has only one db instance running which finabrodb and nothing else is running on this system. The other Db psentry was also my mistake from UAT system sorry for that.

Code:
root@ABRO-DB/#lsattr -El mem0
ent_mem_cap           I/O memory entitlement in Kbytes           False
goodsize       204800 Amount of usable physical memory in Mbytes False
mem_exp_factor        Memory expansion factor                    False
size           204800 Total amount of physical memory in Mbytes  False
var_mem_weight        Variable memory capacity weight            False
root@ABRO-DB/#

For so many archive processes this need to check with dba.
the FILESYSTEMIO_OPTIONS=SETALL is not enabled. The SGA is 40Gb
I have already raise request to increase the SGA to 80Gb as memory is of 200Gb.


Moderator's Comments:
Mod Comment Please use CODE tags correctly as required by forum rules!

Last edited by RudiC; 01-16-2017 at 05:43 AM.. Reason: Changed ICODE to CODE tags.
# 19  
Old 01-17-2017
Quote:
Originally Posted by powerAIX
T
I have already raise request to increase the SGA to 80Gb as memory is of 200Gb.
OK, but prepare to either shrink the LPARs memory or increase the SGA further to about 90% of the available RAM.

The most imminent thing to do, though, is to set the "FILESYSTEMIO_OPTIONS=SETALL" option or to mount the filesystems accordingly. I suggest doing it in the DB configuration: without this you will always have the OS trying to (double-) buffer the DB I/O, which will always be detrimental to performance.

Mounting an FS in CIO-mode (concurrent-I/O) will make all the I/O on that FS be via concurrent I/O, which is a good idea for DB files opened by the DB but a bad idea otherwise. You would need to create separate FSes (not to be mounted with the CIO-option) for i.e. dumps, exports, etc.. Setting the option in the Oracle-config will make the database open the individual files with the CIO-option but the FS itself is not changed. Thiw will have the same effect as above but without the need to create separated FSes.

I hope this helps.

bakunin
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