From the
IP User's Guide and Commands manual for version 2.1 of z/OS:
Before you specify a (+nnn) value to create a new GDS, issue the following command:
SITE DCBDSN=model
This subcommand specifies an MVS™ data set to be used as a model. The model must have a DSORG of PS. The other DCB characteristics of the data set are not checked.
Notes:
Failure to have a valid DCBDSN before trying to create a new GDS might cause FTP or ALLOCATION to fail or to return unpredictable results.
If you issue a SITE DCbdsn LRecl BLKsize command before the creation of a new data set, the LRecl and BLKsize parameters on the SITE command override the LRecl and BLKsize parameters on the DCbdsn command.
Depending upon your FTP, you may need LOCSITE instead of SITE. And you may need to put QUOTE before either command. It is not clear how you expect the MGET to work -- do you think each retrieved file from the server system will be a new generation?