If a data set name is used several times in a job, copy it from
the DD statement that uses it first. It can be copied whether it is
specified in the DSNAME parameter or assigned by the system. Use
copying to make changing data sets from job to job easier and to eliminate
having to assign names to temporary data sets. Copy a data set name
by coding:
//ddname DD DSNAME=*.ddname
//ddname DD DSNAME=*.stepname.ddname
//ddname DD DSNAME=*.stepname.procstepname.ddname
Example
//COPYDS DD DSNAME=*.MYDS