The client found that they no longer had their //CAISDB DD file (....DSCRDB) on the system and we are unable to restore it.
They also lost their ...AR and ...RDM files.
The client used the DSEXQFIX procedure to create a new ...DSCRDB file, for the scratch records.
They restored their AR and RDM files, which had (somehow) been deleted.
With the above, they were able to get the Dispatch task started.