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Conference iosg::all-in-1_v30

Title:	OLD ALL-IN-1 (tm) Support Conference
Notice:	Closed - See Note 4331.l to move to IOSG::ALL-IN-1
Moderator:	IOSG::PYE

Created:	Thu Jan 30 1992
Last Modified:	Tue Jan 23 1996
Last Successful Update:	Fri Jun 06 1997
Number of topics:	4343
Total number of notes:	18308

173.0. "EM: Why is SDAF opened twice per user process?" by COPCLU::RUNE (Rune Gottschalk @DMO) Thu Mar 05 1992 09:03

  Hi,
  
  My customer is running ALL-IN-1 V2.4 in a cluster. The ALL-IN-1 performance 
  is quite bad due to heavy disk activities on the ALL-IN-1 disk, which is 
  also used for other applications. They have a total number of 500 
  concurrent users (1/3 per node) and are using global buffers on their data 
  files (SDAF = 168). He is only using one SDAF file which we are going to 
  change as well !
  
  When I had a look at his installation last time and did a SHOW 
  DEVICE/FILES on the ALL-IN-1 disk, I saw that the SDAF file was opened 
  twice per user. How do we explain that ?
  
  Rune
  EIS/Denmark

T.R Title User Personal
Name Date Lines

173.1 Locking and non-locking AIMTEC::PORTER_T Terry Porter, ALL-IN-1 Support, Atlanta CSC Thu Mar 05 1992 16:05 34

T.R	Title	User	Personal Name	Date	Lines
173.1	Locking and non-locking	AIMTEC::PORTER_T	Terry Porter, ALL-IN-1 Support, Atlanta CSC	`Thu Mar 05 1992 16:05`	34
	For performance reasons ALL-IN-1 prefers to avoid RMS locking, that's OK if no-one is changing the record in question, but a potential disaster if they are. ALL-IN-1 therefore opens 2 channels to the SDAF, one without locking and the second one with and uses the appropriate channel for the operation underway. It can also open a third channel when accessing an attachment!! Opening multiple channels is more efficent than opening and closing one channel frequently for the different modes of access. If your disk drive is overloaded then look at moving some of the files to another drive. Typically the best candidate for the move is the SDAF, which often needs it's own disk when the I/O trafic gets large. Other prime candidates are OA$DATA:PROFILE.DAT and OA$DATA:PENDING.DAT. If there are shared directories or user directories on the same disk then look at spreading them over multiple spindals. The important shared directories are the ones in the write window. The above is just a few pointers on some of the more frequently seen I/O bottlenecks, tuning an ALL-IN-1 system is a more complex exercise, however the performance bottlenecks differ little from any other large I/O bound application. Where ALL-IN-1 knowledge is needed is in deciding the best way to resolve the bottlenecks found. Sounds like you have a good consulting oppertunity here. Regards, Terry

For performance reasons ALL-IN-1 prefers to avoid RMS locking, that's OK if 
no-one is changing the record in question, but a potential disaster if they
are.

ALL-IN-1 therefore opens 2 channels to the SDAF, one without locking and the
second one with and uses the appropriate channel for the operation underway.

It can also open a third channel when accessing an attachment!!

Opening multiple channels is more efficent than opening and closing one
channel frequently for the different modes of access.

If your disk drive is overloaded then look at moving some of the files to
another drive.

Typically the best candidate for the move is the SDAF, which often needs it's
own disk when the I/O trafic gets large. Other prime candidates are 
OA$DATA:PROFILE.DAT and OA$DATA:PENDING.DAT.

If there are shared directories or user directories on the same disk then look
at spreading them over multiple spindals. The important shared directories
are the ones in the write window.

The above is just a few pointers on some of the more frequently seen I/O
bottlenecks, tuning an ALL-IN-1 system is a more complex exercise, however
the performance bottlenecks differ little from any other large I/O bound
application. Where ALL-IN-1 knowledge is needed is in deciding the best way 
to resolve the bottlenecks found.

Sounds like you have a good consulting oppertunity here.

Regards,

Terry