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In this Document

Goal

Fix

Applies to:

Goal

 This document shows the values set per VSM microcode for chain breaking, also called Sync Sort changes.

Fix

Some sort and/or back-up utilities are used in zOS MainFrame that use long command chains to improve efficiency.  The VSM product will break the long chains of commands at specific intervals to facilitate execution of other applications that are waiting for processor time within the VSM to become available.

VSM engineering came up with different values of execution time and break time in different release of VSM Mocrocodes. The following explains the idea behind it and values in various Micrcodes for VTSS are explained below:

Values are used in an attempt to stop one application from acquiring then maintaining control of one of the interfaces in the VTSS. This is accomplished by breaking the command chaining sequence thus allowing another application to use the interface.

D02.04 : wrt chain break = 15ms for first then every 5ms
rd chain break = no break

D02.05 : wrt chain break = 15ms then every 5ms
rd chain break = none

D02.06 : wrt chain break = 25ms for first then every 25ms
rd chain break = no break

D02.07 : wrt chain break = 15ms for first then every 5ms
rd chain break = no break

D02.08 : wrt chain break = 15ms for first then every 5ms
rd chain break = no break

D02.09 : wrt chain break = 15ms for first then every 5ms
rd chain break = add break at 15ms

ZD2.09.11.00 : wrt chain break = 25ms for first then every 25ms
rd chain break = every 25ms Best strategy if customers wants sync sort to run best by sacrificing run time of other applications.

D02.10 : wrt chain break = 15ms for first then every 5ms
rd chain break = break at 15ms

ZD2.10.11.00 : wrt chain break = 15ms for first then every 5ms
rd chain break = break at 15ms

D02.11 : wrt chain break = 15ms for first then every 5ms
rd chain break = break at 15ms

D02.12: wrt chain break = 15ms for first then every 5ms
rd chain break = break at 15ms

D02.14 and later codes : Chain Break Option from DOP - this feature, primarily for the VSM4(but not limited to), provides the ability to modify the command chain breaking algorithm dynamically thru the DOP Configuration screen.

There are three chain break settings - HIGH. MEDIUM, and LOW.

The HIGH setting is the default and will break long command chains more frequently allowing shorter chain jobs a better chance to run.

The MEDIUM setting forces a balanced chain break that does not favor long or short chain jobs.

The LOW setting breaks the chain least frequently allowing the jobs like SyncSort and DB2 to run at their max rate without being interrupted.

The actual chain breaking values for these settings are as follows:

HIGH:
    wrt chain break = 15ms for first then every 5ms
    rd chain break = 15ms for first then every 5ms

MEDIUM:
    wrt chain break = 25ms for first then every 15ms
    rd chain break = 25ms for first then every 15ms

LOW:
    wrt chain break = 100ms for first then every 100ms
    rd chain break = 100ms for first then every 100ms

Changing the break setting is immediate and does not require any other action.

4-25-2011- BF – Created
3-15-2013- DL - Update with D02.14 break values for high, medium and low settings.

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