This article explains how the recovery file RXX can be created on disk instead of tape.
If DYNAM/FI is used then the recovery file can go on disk.
Define the recovery file in the DYNAM catalog with DYNAMFI=YES.
Datacom uses a tape DTF (DTFMT) to open the recovery file but DYNAM/FI changes this into a disk DTF.
FI stands for File Independence.
See the DYNAM/D User Guide here .