Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

AIX (DSCR) and oracle prefetching

Posted on 2014-01-22
6
Medium Priority
?
1,336 Views
Last Modified: 2014-01-22
what is AIX (DSCR) prefetching and how it works with Oracle?
our prod DB is showing:
dscrctl -q
Current DSCR settings:
        Data Streams Version  = V2.06
        number_of_streams     = 12
        platform_default_pd   = 0x4 (DPFD_MEDIUM)
       os_default_pd         = 0x0 (DPFD_DEFAULT)

what does this mean?
0
Comment
Question by:it-rex
  • 3
  • 3
6 Comments
 
LVL 68

Accepted Solution

by:
woolmilkporc earned 2000 total points
ID: 39801187
Hi,

DSCR is hardware memory prefetch. It sometimes can improve the performance of applications, if they reference memory sequentially.

Oracle does not often perform sequential memory access, in fact Oracle's memory access is said to be "irregular", so aggressive prefetching can have an adverse effect on performance because the prefetched lines might not be referenced. Your setting is not very aggressive, though.

I must admit that I'm not a true Oracle tuning specialist, so be careful with the following.

If you're currently experiencing bad performance you could run this command

dscrctl -b -n -s 1

which will turn off memory prefetching (-b = persist across reboots, -n = apply changes immediately, -s 1 = set the dscr value to 1, which is DFPD_NONE).
Please watch the DB very thoroughly for the effect of this setting, and should you see a decrease in performance turn prefetching on again with

dscrctl -b -n -s 0

which will go back to your defaults.

wmp
0
 
LVL 11

Author Comment

by:it-rex
ID: 39801230
so what is the difference between
 os_default_pd         = 0x0 (DPFD_DEFAULT)
and the default of
 os_default_pd         = 0x5 (DPFD_DEFAULT)

?
0
 
LVL 11

Author Comment

by:it-rex
ID: 39801242
Sir..
Also i'm posting few AIX specific Q's and I really like to see your input about them..
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 
LVL 68

Expert Comment

by:woolmilkporc
ID: 39801328
0x0 sets os_default to platform_default, which is 0x4 DPFD_MEDIUM fot the machine shown in your question.

0x5 is not DPFD_DEFAULT, and also not platform_default, at least not on the machine you showed in your Q. There are machines whose platform_default is 0x5, but DFPD_DEFAULT is always 0x0!
0x5 is DFPD_DEEP, which is more aggressive than DPFD_MEDIUM
0
 
LVL 11

Author Comment

by:it-rex
ID: 39801351
so what do you suggest here?
0
 
LVL 68

Expert Comment

by:woolmilkporc
ID: 39801371
Leave it at 0x0 (the default which is DFPD_MEDIUM in your case) or turn it off according to my first comment - please read it again - in full!
0

Featured Post

Upgrade your Question Security!

Your question, your audience. Choose who sees your identity—and your question—with question security.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When you do backups in the Solaris Operating System, the file system must be inactive. Otherwise, the output may be inconsistent. A file system is inactive when it's unmounted or it's write-locked by the operating system. Although the fssnap utility…
Every server (virtual or physical) needs a console: and the console can be provided through hardware directly connected, software for remote connections, local connections, through a KVM, etc. This document explains the different types of consol…
This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.
In a previous video, we went over how to export a DynamoDB table into Amazon S3.  In this video, we show how to load the export from S3 into a DynamoDB table.
Suggested Courses

577 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question