Just curious. I'm looking at:
z/OS 2.2.0
z/OS DFSMS
z/OS DFSMS Using Data Sets
Non-VSAM Access to Data Sets and UNIX Files
Processing a Partitioned Data Set Extended (PDSE)
Creating a PDSE Member
Adding or Replacing Multiple PDSE Members Concurrently
... which makes it pretty clear that multiple DCBs are required (else how
would the access method know which member to write?)
The example appears to show that all (both) the DCBs can use the same
DDNAME, "X" in the example. "X" is a confusing choice because "X" is
often used to imply "indeterminate".
Since Allocate and OPEN are both considered costly, it's valuable to
minimize the number of each. Apparently as many OPENs are needed
as members are being written concurrently.
The example is in Assembler. What other languages support this?
I know support for BPAM by IBM programming languages is limited.
Some ISVs do better, supporting the form ddname(member) in
addition to the two IBM supports, ddname and dsname(member).
Rexx? I suppose I'd need a separate allocation for each member?
ISPF LM Services? I see:
z/OS 2.2.0
ISPF
z/OS V2R2 ISPF Services Guide
Description of the ISPF services
LMOPEN-open a data set
"It is the responsibility of the dialog developer to ensure that
a data set is opened for output only once."
Apparently not. But can the programmer issue multiple LMINITs
on one DDNAME, getting a unique DATA-ID for each, then interleave
LMPUTs to the various DATA-IDs?
Or suppose an EDIT macro updates a member of the same PDSE, but
a different member from the one being edited? Should be easy: I
believe EDIT does no actual I/O until a SAVE.
Can an EDIT macro infer the DDNAME ISPF is using and issue the
LMINIT against that, avoiding the costly allocation?
Just curious,
gil
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