Ddname allocation allows you to reuse, by specifying only the associated ddname, a previously allocated data set that was marked not-in-use. Ddname allocation causes the system to assign the in-use attribute to the data set.
You request dynamic allocation by ddname by specifying verb code 06 and putting the ddname to be allocated in the DYNALLOC macro parameter list. For the system to satisfy your ddname dynamic allocation request, the existing allocation must not be in use. In addition, it must not have the convertible attribute; or it must be permanently concatenated. In other words, it must have properties that ensure that the ddname could not have been disassociated from the existing allocation. (See Requesting the permanently concatenated attribute for a description of this attribute.)
If the existing allocation with the specified ddname does not meet these requirements, or if the ddname is not associated with any of your program's existing allocations, the system fails the request and returns an error reason code in the SVC 99 parameter list.
If the existing allocation meets the requirements, the system assigns it the in-use attribute and the request has been satisfied. If the existing allocation is a member of a concatenated group, all members of the group are assigned the in-use attribute, so the entire group has been allocated.
To request that the system return an indication of whether the existing allocation that satisfies the request is associated with a dummy data set, use verb code 6 with key 2.