An I/O data set must first be allocated to a ddname. The ddname need not exist previously. In fact, it might be better to allocate it to a new ddname, such as MYINDD, in order not to interfere with previously established allocations. You can allocate before the exec runs, or you can allocate from within the exec with the ALLOCATE command as shown in the following example.

"ALLOC DA(io.data) F(myindd) SHR REUSE"
"EXECIO  *  DISKR  myindd  (FINIS"