Several varieties of partitioning programs have been adapted by Debian developers to work on various types of hard disks and computer architectures. Following is a list of the program(s) applicable for your architecture.
Recommended partitioning tool in Debian. This Swiss army knife can also resize partitions, create filesystems and assign them to the mountpoints.
S/390 version of fdisk; Please read the fdasd manual page or chapter 13 in Device Drivers and Installation Commands for details.
One of these programs will be run by default when you select(or similar). It may be possible to use a different partitioning tool from the command line on VT2, but this is not recommended.