Memorex LOCK - VERSION 2-24 Informacje Techniczne Pobierz pdf (Strona 329)

100

101

Choosing the Device Type

User Reference

Use Pursuant to Company Instructions

7-61

Choosing the Device Type

Description Generic Device Independence (GDI) and Generic Device Independence

for Unit Record Devices (GDIUR), sometimes called storage media

independence, allow you to choose the type of media on which your

dataset will be stored.

With GDI, you can process the dataset on either tape or disk, without

having to change the media type in the program’s dataset definition.

GDIUR allows you to use disk or tape for datasets that have been defined

in your programs as unit record devices, for example DTF types DTFCD,

DTFPR, DTFCP, and DTFDI. GDIUR can be used for logical units

SYS000 through SYS255 and for SYSIPT, SYSLST, and SYSPCH.

GDIUR greatly simplifies the use of disk for VSE datasets that use the

logical units SYSIPT, SYSLST, and SYSPCH. The following standard

VSE JCL is an example of creating a disk dataset on logical unit SYSPCH

and then reading that dataset with logical unit SYSIPT.

// DLBL IJSYSPH,'COBOL.PROGRAM',0

// EXTENT SYSPCH,VOL251,1,0,200,2000

ASSGN SYSPCH,DISK,VOL=VOL251,SHR

// EXEC DFHECP1$

CLOSE SYSPCH,PUNCH

// DLBL IJSYSIN,'COBOL.PROGRAM'

// EXTENT SYSIPT,VOL251

ASSGN SYSIPT,DISK,VOL=VOL251,SHR

// EXEC FCOBOL

CLOSE SYSIPT,SYSRDR

There are two issues when using this approach.

 If the first step (DFHECP1$) cancels, SYSPCH will remain

permanently assigned to disk. Manual intervention or additional

JCL is needed to re-assign SYSPCH correctly.

 If the second step (FCOBOL) cancels, SYSIPT remains

permanently assigned to disk. Manual intervention or additional

JCL is needed to re-assign SYSIPT correctly.

In addition, the JCL required is complex and lengthy, especially when

compared to the following BIM-EPIC JCL which accomplishes the same

task.

* //IJSYSPH DD DSN=$$$.COBOL,UNIT=DISK,DISP=(,KEEP,DELETE)

// EXEC DFHECP1$

//IJSYSIN DD DSN=$$$.COBOL,DISP=(OLD,DELETE)

// EXEC FCOBOL

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