Do i need to increase RA_xx parameters? 
Author Message
 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

==================================
Poster's IP address: 212.15.12.4
Posted via http://www.***.com/
Linux Programmer's Site



Fri, 19 Mar 2004 19:42:22 GMT
 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.

Quote:
-----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

==================================
Poster's IP address: 212.15.12.4
Posted via http://nodevice.com
Linux Programmer's Site

==========================================================
This message contains information intended for the perusal, and/or use (if
so stated), by the stated addressee(s) only. The information is
confidential and privileged. If you are not an intended recipient, do not
peruse, use, disseminate, distribute, copy or in any manner rely upon the
information contained in this message (directly or indirectly). The sender
and/or the entity represented by the sender shall not be held accountable
in the event that this prohibition is disregarded. If you receive this
message in error, notify the sender immediately by e-mail, fax or telephone
representations contained in this message, whether express or implied, are
those of the sender only, unless that sender expressly states them to be
the views or representations of an entity or person, who shall be named by
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==========================================================



Fri, 19 Mar 2004 23:17:33 GMT
 Do i need to increase RA_xx parameters?

However,  If you are doing DSS....

RA determines the number of light scan buffer pools you get.  Max them out.

cheers
j.

Quote:
----- 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

> ==================================
> Poster's IP address: 212.15.12.4
> Posted via http://nodevice.com
> Linux Programmer's Site

> ==========================================================
> This message contains information intended for the perusal, and/or use (if
> so stated), by the stated addressee(s) only. The information is
> confidential and privileged. If you are not an intended recipient, do not
> peruse, use, disseminate, distribute, copy or in any manner rely upon the
> information contained in this message (directly or indirectly). The sender
> and/or the entity represented by the sender shall not be held accountable
> in the event that this prohibition is disregarded. If you receive this
> message in error, notify the sender immediately by e-mail, fax or
telephone
> representations contained in this message, whether express or implied, are
> those of the sender only, unless that sender expressly states them to be
> the views or representations of an entity or person, who shall be named by
> the sender and who the sender shall state to represent. No liability shall
> otherwise attach to any other entity or person.
> ==========================================================



Sat, 20 Mar 2004 00:02:34 GMT
 
 [ 3 post ] 

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