DFSMShsm supports the creation of a duplicate cartridge tape, called an alternate, for each migration tape or each backup tape. The major use of this is to support remote storage of the alternate so that it can easily be used in case of a disaster.

The recommended process includes these steps related to tape usage:

1. Have a copy of the DFSMShsm control data sets at the disaster site.
2. Perform a TAPEREPL by specifying the DISASTERALTERNATE parameter. This flags each existing alternate tape as a disaster alternate.
3. Place DFSMShsm in DISASTER mode. When in disaster mode DFSMShsm dynamically checks before mounting an input tape whether the needed data resides on a tape having a disaster alternate. If it does, the disaster alternate is requested.

DFSMSrmm recognizes when DFSMShsm is opening tape data sets and tolerates the data set names that DFSMShsm uses as long as the last 17 characters of the data set name match.

When you perform a true replacement by using the TAPEREPL command, without the DISASTERALTERNATE keyword, DFSMShsm uses the data set name it uses for the original tapes.