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Control OperationsDay 5

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#Copyright 2005,Infosys Technologies Ltd

ER/CORP/CRS/TP01/003Version No: 1.0

Objectives Task Control

ENQUEUE/DEQUEUE

SUSPEND

Program Control Usage of COMMAREA in LINK, XCTL

RETURN

LOAD, RELEASE

Storage Control GETMAIN

FREEMAIN

Interval Control ASKTIME, FORMATTIME

START, ATI

CANCEL, RETRIEVE

DELAY, POST, WAIT EVENT

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Task Control

SUSPEND Suspend a task

To relinquish control to a task of higher dispatching priority

Control returns to the task issuing the command when there is no other

task of higher priority to be processed

ENQ/DEQ Schedule the use of a resource by a task

Protects the resource from concurrent use by more than one task

ENQ

RESOURCE (data-area)

[LENGTH (data-value)]

[NOSUSPEND]

Conditions: ENQBUSY, LENGERR

DEQRESOURCE (data-area)

[LENGTH (data-value)]

Conditions: LENGERR

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Program Control Commands

XCTL LINK

RETURN

ABEND LOAD

RELEASE

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Logic Levels

CICS

PGM ALINK B

RETURN

PGM C

LINK DRETURN

PGM B

XCTL C

PGM D

RETURN

LEVEL 0

LEVEL 1

LEVEL 2

LEVEL 3

CICS

PGM ALINK B

RETURN

PGM C

LINK DRETURN

PGM B

XCTL C

PGM D

RETURN

LEVEL 0

LEVEL 1

LEVEL 2

LEVEL 3

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XCTL

EXAMPLEEXEC CICS XCTLPROGRAM (example3)

COMMAREA (ws-commarea)

LENGTH (100)

END-EXEC.

This causes control to be passed to example3,

with 100 bytes of data.

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LINK

EXAMPLEEXEC CICS LINKPROGRAM (example3)

COMMAREA (ws-commarea)

LENGTH (100)

END-EXEC.

The calling program expects control back.

Control to example3 with 100 bytes of data.

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XCTL Vs LINK

XCTL does not expectcontrol back.

Handle conditions in the

main program are not

available to the calledprogram. Establish new

handle conditions.

LINK expects controlback.

Handle conditions in the

calling program are

needed again. Hence usePUSH and POP

commands to restore

them again.

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XCTL Vs LINK Continues...

XCTL does not expectcontrol back and hence

less overhead on system

resources like memory

etc. Similar to GO TO.

LINK expects controlback and hence the

overhead is more in this

case on memory etc.

Similar to perform, andcontrol will be passed

back to the instruction

following this.

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CALL Vs XCTL/LINK

Linkedited along withthe main module.

Higher module size and

higher memory

requirement. Single copy can not be

used.

Separately compiled andlink edited.

Single copy be shared.

Dynamic loading may

slow down executionspeed.

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CALL Vs XCTL/LINK Continues...

Any changes in thisrequire compiling of all

other modules using this.

A CALLed program

remains in the last usedstate after it returns

control.

Changes in this will noteffect other modules

using this.

A LINKed or XCTLed

program always brings aNEW copy.

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RETURN

Return, always passes control back to the

program at one logic level higher when used

without any options.

Return with TRANSID option passes control toanother program, in pseudo-conversation mode.

It is important to note that RETURN is not at all

a replacement for LINK or XCTL.

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ABEND

When a situation arises that the program can nothandle the program condition, can terminate

itself by giving an abend code to help the user.EXEC CICS ABEND

ABCODE (abcd)

END-EXEC.

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Storage Control

GETMAIN - to get main memory

FREEMAIN - to release the memoryacquired by GETMAIN

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Interval Control

ASKTIME

FORMATTIME START

CANCEL

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Interval Control Continues...

START can be used for starting a Transactionfrom a remote terminal.EXEC CICS START

TRANSID (TA01)

[INTERVAL (hhmmss)/TIME (hhmmss)]

[TERMID (terminal-no)]END-EXEC.

CANCEL command can be used to cancel the

interval control commands given previously.

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Interval Control Continues...

ASKTIME [ABSTIME (data-area)]

FORMATTIME

ABSTIME (data-value)

[YYDDD (data-area)]

[YYMMDD (data-area)]

[YYDDMM (data-area)]

[DDMMYY (data-area)]

[MMDDYY (data-area)]

[DATE (data-area)]

[DATEFORM (data-area)]

[DATESEP [(data-area)]]

[YEAR (data-area)]

[TIME (data-area)

[TIMESEP [(data-area)]]

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Summary

What are the task control statements and whatare they used for?

What is the difference between XCTL and

LINK?

How is CALL different from XCTL and LINK?

Why is RETURN used?

What are the commands for Storage control? How can we format the date and time from the

system?

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Thank You!

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Ppt Tp01 Cics 05