Depending on the IP configuration setup into a file called FTP.DATA or FTPSDATA. The default LRECL is 128 and the default RECFM is VB if the system programmer does not change any of the defaults. The file also controls things like the default space allocation size and type (trk vs.cyl) and whether the default FTP environment is z/OS MVS or z/OS Unix.
The best way to ensure you always get the file format you want is to use the SITE or LOCSITE commands prior to issuing a GET or PUT in your FTP process.
If you are doing a GET from the mainframe you would use LOCSITE prior to the GET.
If you were doing a PUT from another platform to the mainframe, you would use the SITE command - which you need to send via "QUOTE SITE".
Here is an example of doing a GET from an FTP batch job on the mainframe to download from CA Support site a product :
//FTP JOB (ACCT),CLASS=A,...
//STEP1 EXEC PGM=FTP,REGION=4M,PARM='(EXIT'
//SYSPRINT DD SYSOUT=*
//OUTPUT DD SYSOUT=*
//INPUT DD *
cd case number
get DVD02142159E.pax.Z /a/CAI/DVD02142159E.pax.Z (REPLACE
locsite LRECL=80 BLKSIZE=27920 RECFM=FB
locsite CYL PRIMARY=100 SECONDARY=20
For more information on using FTP on z/OS see the z/OS V2R3.0 Communications Server: IP User's Guide and Commands
You can also have a look to this book TCP/IP Tutorial and Technical Overview - IBM Redbooks
CA Knowledge document https://ca-broadcomcsm.wolkenservicedesk.com/wolken/esd/knowledgebase_list?articleId=10398