However, If you are doing DSS....
RA determines the number of light scan buffer pools you get. Max them out.
----- Original Message -----
Sent: Monday, October 01, 2001 11:17 AM
Subject: RE: Do i need to increase RA_xx parameters?
> Something I found on the web somewhere (Tech Notes I think), compliments
of
> Art Kagel -
> E. RA_PAGES, RA_THRESHOLD. Faster systems, especially systems with faster
> disk farms, need less read ahead. These values, and their utility to us,
is
> heavily dependent on I/O speed. If you use discrete drives look to set
> RA_PAGES around 64 with a large threshold of between 16 and 32. If you are
> using a large RAID10 configurations, with a stripe of many pairs of
mirrored
> 10000RPM drives, using a caching controller capable of its own read ahead,
> you can run a very busy system with RA_PAGES=16 and RA_THRESHOLD=4.
> Onstat -p reports on read ahead usage stats. The sum of idx-RA, idxda-RA,
> and da-RA should be very close to the value of RA-pgsused. Increase these
> parameters until the ratio drops or the read-cache% begins to drop.
> Excessive read-ahead can cause needed data buffers to be flushed, causing
> the drop in read-cache%. This can happen even while the RA ratio is
> improving, so be careful to balance these. If this happens, either back
off
> on the RA parameters until the read-cache% is again acceptable, or
increase
> the number of buffers until the read-cache% improves.
> -----Original Message-----
> Sent: Monday, October 01, 2001 1:42 PM
> Subject: Do i need to increase RA_xx parameters?
> Dear Informix Community,
> I have the following onstat outputs:
> Informix Dynamic Server 2000 Version 9.21.FC4 -- On-Line -- Up
> 03:59:36 -- 5126144 Kbytes
> Profile
> dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
> 9119308 62087177 674286865 98.65 1446173 2724607 9490173 84.76
> isamtot open start read write rewrite delete commit
> rollbk
> 643153602 32531343 30892874 439061200 1300891 767955 37420 279198
> 60159
> gp_read gp_write gp_rewrt gp_del gp_alloc gp_free gp_curs
> 0 0 0 0 0 0 0
> ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes
> 9 0 0 120380.10 16773.26 41 82
> bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans
> 1122116 7508 546211790 1914 0 4294 448623 228280
> ixda-RA idx-RA da-RA RA-pgsused lchwaits
> 1862503 373399 983593 3109602 2977112
> I have 228280 seq.scans in 4 hours (which means 15 per second.)
> I want to know whether these sequental scans are good or bad and i query
> sysptprof table.
> I want to ask , if my sequental scans are good do i need to increase my RA
> parameters?
> The number of diskreads are:9,119,308 and number of RA-pgsused :
3,109,602
> (nearly 1/3) . and the totals of ixdaRa,idxRa,daRA is
> 3,219,495. Do i need to increase RA pages?They are currently in default
> values.
> Kind Regards,
> hope
> ==================================
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> Linux Programmer's Site
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Do i need to increase RA_xx parameters?