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Oracle Tips by Burleson

Disk I/O Tuning

Chapter 3: HP-UX SCSI Tuning

Much like SUN Solaris, HP has several kernel based tuning parameters that are used to adjust the behavior of to SCSI interface, bus and device.

Probably, the most important is scsi_max_qdepth.

scsi_max_qdepth - This is the maximum number of I/Os that a single SCSI target will queue up for execution.  The parameters has a minimum value of 1, a default set value of 8, and a maximum value of 255.

Some SCSI devices support tagged queuing, which means they can have more than one SCSI command outstanding at any point in time.  The number of commands that can be outstanding varies by device and is not known to HP-UX.  To avoid overflowing this queue, HP-UX will not send more than a certain number of outstanding commands to any SCSI device.  This tunable sets the default value for that limit.  The default value can be overridden for specific devices using ioctl.  The ioctl is a device interface system control that allows commands to be issued to alter specific setpoints on devices; it is not a command line program.

The above text is an excerpt from:

Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle Databases
ISBN 0-9745993-4-4 

by Mike Ault

Oracle Consulting Services

Burleson Oracle Consulting offers Senior Oracle consultants which are available for all areas of Oracle support.  Common Oracle consulting support activities include short-term Oracle tuning, Oracle database troubleshooting, Oracle9i and Oracle10g migration, Oracle9iAS App Server consulting, Oracle design reviews and Oracle requirements evaluation support. Oracle support and Oracle consulting services are priced by the hour, so you only pay for what you need. These one-time Oracle consulting services commonly include:

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  • Installation of Oracle application packages

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