GDG Version

[T-Bonham@scc.net]

I seem to recall from long ago that the OS will return these generations in order of the most recently cataloged first.

Which can lead to a rather obscure bug, if your logic depends on them being in a specific order.

If you have GDG Base: MDMX000.BS100.GDG
Version 1: MDMX000.BS100.GDG.G0001V00
Version 2: MDMX000.BS100.GDG.G0002V00
Version 3: MDMX000.BS100.GDG.G0003V00
Version 4: MDMX000.BS100.GDG.G0004V00
Version 5: MDMX000.BS100.GDG.G0005V00

But a recent fix created & cataloged a new version of generation 3, thus now:
Version 3: MDMX000.BS100.GDG.G0003V01
then the order they will be returned in is
1st: MDMX000.BS100.GDG.G0003V01
2nd: MDMX000.BS100.GDG.G0005V00
3rd: MDMX000.BS100.GDG.G0004V00
4th: MDMX000.BS100.GDG.G0002V00
5th: MDMX000.BS100.GDG.G0001V00

Can anyone confirm if this is correct, or am I remembering it wrong?

(In any case, the smart way to program this is to make it independent of the order of the input, either by reading an appropriate date off a header record or a data field on each record, or by sorting the input as needed before the program, or some similar programming technique.)

[stefan]

Originally Posted by T-Bonham@scc.net

Can anyone confirm if this is correct, or am I remembering it wrong?

I think you're wrong. Look at this job:

//* --------------------------------------------------------------- *//
//DEFINE   EXEC PGM=IDCAMS                                             
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  *                                                       
 DELETE INT1098.GDG.*                                                  
 DELETE INT1098.GDG GDG                                                
 DEFINE GDG(NAME('INT1098.GDG') SCRATCH LIMIT(3))                      
 SET MAXCC=0                                                           
/*                                                                     
//* --------------------------------------------------------------- *//
//CREATE1  EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  *                                                       
FIRST                                                                  
//SYSUT2   DD  DSN=INT1098.GDG(+1),DISP=(NEW,CATLG,DELETE),            
//             LRECL=80,BLKSIZE=0,RECFM=FB,DSORG=PS,SPACE=(TRK,(1))    
/*                                                                     
//* --------------------------------------------------------------- *//
//CREATE2  EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  *                                                       
SECOND                                                                 
//SYSUT2   DD  DSN=INT1098.GDG(+2),DISP=(NEW,CATLG,DELETE),            
//             LRECL=80,BLKSIZE=0,RECFM=FB,DSORG=PS,SPACE=(TRK,(1))    
/*                                                                     
//* --------------------------------------------------------------- *//
//CREATE3  EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  *                                                       
THIRD                                                                  
//SYSUT2   DD  DSN=INT1098.GDG(+3),DISP=(NEW,CATLG,DELETE),            
//             LRECL=80,BLKSIZE=0,RECFM=FB,DSORG=PS,SPACE=(TRK,(1))    
/*                                                                     
//* --------------------------------------------------------------- *//
//CONCAT1  EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  DISP=SHR,DSN=INT1098.GDG                                
//SYSUT2   DD  SYSOUT=*                                                
/*                                                                     
//* --------------------------------------------------------------- *//
//DELETE   EXEC PGM=IDCAMS                                             
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  *                                                       
 DELETE INT1098.GDG.G0002V00                                           
/*                                                                     
//* --------------------------------------------------------------- *//
//CREATE2N EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  *                                                       
SECOND (FIXED)                                                         
//SYSUT2   DD  DSN=INT1098.GDG.G0002V01,DISP=(NEW,CATLG,DELETE),       
//             LRECL=80,BLKSIZE=0,RECFM=FB,DSORG=PS,SPACE=(TRK,(1))    
/*                                                                     
//* --------------------------------------------------------------- *//
//CONCAT2  EXEC PGM=IEBGENER                                           
//SYSPRINT DD  SYSOUT=*                                                
//SYSIN    DD  DUMMY                                                   
//SYSUT1   DD  DISP=SHR,DSN=INT1098.GDG                                
//SYSUT2   DD  SYSOUT=*                                                
/*                                                                     
//                                                                     

The output on SYSUT2 of step CONCAT1 is as follows:

THIRD
SECOND
FIRST

That's the concatenation as expected (youngest first).
Now look at the output at SYSUT2 of step CONCAT2:

THIRD
SECOND (FIXED)
FIRST

As you see, nothing has changed although the second generation has been deleted and recreated and thus is the "youngest" one.