Alter GDG file

The maximum limit of a GDG file is 255 generations.

Say, you have created a GDG base with the limit of 50 generations and later you want to increase its limit to maximum (255 generations), then you need to Alter GDG base like below.

//STEP01 EXEC PGM=IDCAMS      
//SYSPRINT DD SYSOUT=*        
//SYSIN    DD *               
  ALTER GDG.BASE.NAME LIMIT(255)
/*

Once the above job is successful, the limit of GDG file GDG.BASE.NAME will be increased from 50 to 255.