Mainframe programmers are problem-solvers. In at this time’s massive, advanced information facilities, we’re usually confronted with ad-hoc questions from administration – questions that echo the previous Nationwide Enquirer slogan, “Inquiring Minds Wish to Know.” And administration normally needs solutions proper now:
- What does this dataset appear to be?
- What are its traits?
- How a lot area does it occupy?
- When was it created and final referenced?
For a single dataset, this type of data can normally be obtained with a look at an ISPF panel or two. For an inventory of datasets, although, it’s not so easy. We have to get hold of detailed information for every dataset, presumably preserve monitor of operating totals, and supply a report.
Why REXX and LISTDSI Are a Pure Match
The REXX programming language is right for fixing these kinds of issues, and the REXX LISTDSI perform permits the programmer to simply get hold of all kinds of details about a z/OS dataset.
LISTDSI returns information in effectively over 30 variables that may inform us all the things from the dataset’s group and file size to its encryption key label, variety of listing blocks, and SMS class names.
When utilized in a loop to learn an enter listing of dataset names, LISTDSI variables like SYSALLOC and SYSUSED may be collected to maintain a operating whole of disk area. Different variables, like SYSEXPIRE and SYSUPDATED, can be utilized to establish potential issues – for instance, disk datasets which have expired or have been modified however not backed up.
Operating LISTDSI in TSO or Batch
LISTDSI is a TSO/E exterior perform and should run in a TSO tackle area. That is normally not an issue, nonetheless, because it’s potential to run TSO in batch just by specifying PGM=IKJEFT01.
The only format of LISTDSI is solely a REXX perform specifying the dataset identify, for instance:
x = LISTDSI(the-dataset)
the place ‘the-dataset’ is a variable containing the only dataset identify for which we wish data.
The variable ‘x’, the perform code, is critical as a result of LISTDSI have to be known as as a REXX perform. A zero perform code signifies success, 4 signifies partial success (some however not all information returned), and 16 signifies a failure.
The precise dataset data is positioned in quite a few predefined REXX variables, all of which start with the characters ‘SYS’ – similar to SYSVOLUME, SYSDSORG, SYSRECFM, and so forth. The contents of those variables can then be written out utilizing REXX ‘SAY’ statements or used for different processing within the exec.
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Non-compulsory Parameters That Return Even Extra Element
By default, LISTDSI merely obtains details about the dataset from the catalog and the amount VTOC. Nevertheless, a number of extra parameters can comply with the dataset identify within the LISTDSI name to return additional data, together with listing block counts and SMS class names.
An important of those parameters are:
- RECALL/NORECALL, which controls whether or not DFSMShsm is allowed to recall datasets from archive throughout LISTDSI processing
- SMSINFO/NOSMSINFO, which returns the category names for SMS-managed datasets.
Recognized Limitations to Be Conscious Of
There are, sadly, nonetheless a number of limitations to LISTDSI processing.
No data is returned for tape or Unix Techniques Providers information, and technology dataset names have to be absolutely specified (no relative GDGs). For VSAM datasets, solely a restricted subset of knowledge is returned (SYSVOLUME, SYSUNIT, and SYSDSORG).
It’s potential these drawbacks will likely be eliminated in a future z/OS launch. Even with these limitations, nonetheless, LISTDSI is a very easy technique to get detailed details about z/OS datasets.
That data is returned in easy-to-use REXX variables, and gives a fast means for the programmer – dealing with a sudden demand for information – to offer what’s wanted, when it’s wanted, to fulfill these inquiring managerial minds.
Instance: Displaying Key LISTDSI Variables
The determine under reveals a easy REXX exec that shows a few of the extra attention-grabbing LISTDSI variables for a specified dataset identify, together with the date and time the dataset was created:
Turning LISTDSI Output into Operational Perception
LISTDSI provides mainframe groups a quick, versatile technique to extract crucial dataset particulars utilizing acquainted REXX constructs – making it simpler to reply questions, spot points, and preserve storage data flowing when it issues most.
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