StorageTek 6 manual Excessive Use of VIew Command Affects Performance

Excessive Use of VIew Command Affects Performance

Each time the VIew command is invoked, the automatic functioning occurring within an LSM is interrupted. During the interruption, the robot hands and associated cameras are stopped from performing HSC directed library functions to focus on some specified area within the LSM for some specified time interval. Any manual intervention with library functioning can have a negative effect on the throughput of an LSM and consequently affect overall library performance.

How to Monitor Usage of the VIew Command

There are two facilities available for monitoring use of the VIew command:

•enabling SMF logging

•running and analyzing the Activities Report.

It is highly recommended that you enable recording of the subtype 8 SMF record. After each successful use of the VIew command, a subtype 8 SMF record is written. The record documents the component that was viewed, the view time requested, and the actual view time used. Be aware that the time actually used can be shorter than time requested at the invocation of the command, if the operator responds to the outstanding WTOR before the expiration of the requested time interval. Refer to ‘‘Adding SMF Parameters’’ in the HSC Installation Guide for details on how to specify the SMF parameters.

Note: Subtype 8 SMF record logging is not a default and must be specified in accordance with the instructions contained in the referenced paragraph.

Another useful technique to monitor the use of the VIew command is to run the Activities Report utility and to thoroughly analyze the resulting report. Heavy use of the VIew command results in low levels for performance criteria delineated in an Activity Report. Depending upon system load for the specified time reported in an Activity Report, most performance parameters are adversely affected by excessive use of the command. For example, LSM ARM USE percentages reflected in an Activities Report are most likely to be low during heavy use of the command.

Each successful use of the VIew command is counted as one robotic motion for reliability measuring (R+) purposes. Refer to Appendix D, “Logging ACS Robotics Motion” on page 603 for information on robotic statistics logging.

Advantages of Using the VIew Command

There are definite advantages for using the VIew command as opposed to other alternatives. Obvious benefits for using the command include:

•The VIew command easily permits monitoring of tape drives and other LSM components with the execution of a single command entered at the system console. The LSM does not need to be modified offline to execute the command.

•The operator does not enter the LSM.

•The camera can be focused on a specific component that is considered as suspect; thus, time is saved by avoiding the lengthy process of physically entering the LSM.

420VM/HSC 6.0 System Programmer’s Guide

1st ed., 6/30/04 - 312579601