The value in a file can be replaced in JCL using FINDREP command as shown below:

Sample Input :

Mainframe wordd
Wordd of Mainframe
MainframeWorddly
Hellowordd Mainframe!

FINDREP command can be used to find and replace the contents in the input record. 

//EXEC PGM=SORT
//SYSPRINT DD SYSOUT=*
//SYSOUT   DD SYSOUT=*
//SORTIN   DD DSN=<input file>,
//        DISP=SHR
//SORTOUT  DD DSN=<output file>,
//        DISP=(NEW,CATLG,DELETE)
//SYSIN DD *
  OPTION COPY
  OUTREC FINDREP=(IN=C’Wordd’,OUT=C’World’)
/*

IN and OUT statement can also be replaced by INOUT as below:
 
OUTREC FINDREP=(INOUT=(C’Wordd’,C’World’))

Output

Mainframe wordd
World of Mainframe
MainframeWorldly
Hellowordd Mainframe!