Control Operations Day 5. 2 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/TP01/003 Version No: 1.0 Objectives Task Control –ENQUEUE/DEQUEUE –SUSPEND.

Control OperationsDay 5

2Copyright © 2005, Infosys Technologies Ltd

ER/CORP/CRS/TP01/003 Version 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



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 taskENQ

RESOURCE (data-area)

[LENGTH (data-value)]

[NOSUSPEND]

Conditions: ENQBUSY, LENGERR

DEQ RESOURCE (data-area)

[LENGTH (data-value)]

Conditions: LENGERR



Program Control Commands• XCTL

• LINK

• RETURN

• ABEND

• LOAD

• RELEASE



Logic Levels

CICS

PGM ALINK BRETURN

PGM CLINK DRETURN

PGM BXCTL C

PGM DRETURN

LEVEL 0

LEVEL 1

LEVEL 2

LEVEL 3

CICS

PGM ALINK BRETURN

PGM CLINK DRETURN

PGM BXCTL C

PGM DRETURN

LEVEL 0

LEVEL 1

LEVEL 2

LEVEL 3



XCTL• EXAMPLE

EXEC CICS XCTL

PROGRAM (‘example3’)

COMMAREA (ws-commarea)

LENGTH (100)

END-EXEC.

• This causes control to be passed to ‘example3’, with 100 bytes of data.



LINK• EXAMPLE

EXEC CICS LINK

PROGRAM (‘example3’)

COMMAREA (ws-commarea)

LENGTH (100)

END-EXEC.

• The calling program expects control back.

• Control to example3 with 100 bytes of data.



XCTL Vs LINK• XCTL does not expect

control back.• Handle conditions in the

main program are not available to the called program. Establish new handle conditions.

• LINK expects control back.

• Handle conditions in the calling program are needed again. Hence use PUSH and POP commands to restore them again.



XCTL Vs LINK Continues...• XCTL does not expect

control back and hence less overhead on system resources like memory etc.

• Similar to GO TO.

• LINK expects control back and hence the overhead is more in this case on memory etc.

• Similar to perform, and control will be passed back to the instruction following this.



CALL Vs XCTL/LINK• Linkedited along with

the main module.• Higher module size and

higher memory requirement.

• Single copy can not be used.

• Separately compiled and link edited.

• Single copy be shared.• Dynamic loading may

slow down execution speed.



CALL Vs XCTL/LINK Continues...• Any changes in this

require compiling of all other modules using this.

• A CALLed program remains in the last used state after it returns control.

• Changes in this will not effect other modules using this.

• A LINKed or XCTLed program always brings a NEW copy.



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 to another program, in pseudo-conversation mode.

• It is important to note that RETURN is not at all a replacement for LINK or XCTL.



ABEND• When a situation arises that the program can not

handle the program condition, can terminate itself by giving an abend code to help the user.

EXEC CICS ABEND

ABCODE (‘abcd’)

END-EXEC.



Storage Control

• GETMAIN - to get main memory

• FREEMAIN - to release the memory acquired by GETMAIN



Interval Control

• ASKTIME

• FORMATTIME

• START

• CANCEL



Interval Control Continues...• START can be used for starting a Transaction

from 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.



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)]]



Summary• What are the task control statements and what

are 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?



Thank You!

Control Operations Day 5. 2 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/TP01/003 Version No: 1.0 Objectives Task Control –ENQUEUE/DEQUEUE –SUSPEND.

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