You may receive unexpected allocation amounts when using parameter ALCTYPE=KB or MB on the RLST of the SPACSQTY function

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    MainView SRM Allocation


    MainView SRM Allocation 7.8 and 7.9 and MainView SRM StopX37/II 7.8 and 7.9


    When using ALCTYPE=KB or MB on the RLST set statement for SPACSQTY,  you may receive unexpected allocation amounts from SPACSQTY.




    There are only 4 units you can use to tell MVS how much space to allocate which are: cylinders, tracks, blocks or records.


    The following SET statement is allocated in blocks which is not apparent when looking at just the parms:







    The presence of ALCTYPE=KB indicates that the allocation will be a block allocation and that the primary and secondary being requested is in kilobytes. In looking at the SET statement, it is not apparent as to what the corresponding MVS JCL would look like if SPACSQTY were not used. As it turns out, the JCL would look like this:




    So the equivalent JCL looks nothing like what was specified in the SPACSQTY SET statement.  Another way to say the same thing is, it is difficult to visualize how much space is actually being requested in terms of tracks or cylinders by looking only at the SET parm statements..


    When the allocation type is KB, the code will multiply the primary and secondary values specified in the SET parm by 1024 to get the primary and secondary allocation in bytes. It will then take the average block size specified by the AVL SET parm (which in this case it used the default value of 9000) and will divide that into the results of the multiplication by 1024 done earlier and will use those values for the primary and secondary allocations as the whole objective is to come up with the number of 9000 byte blocks to allocate.


    We are recommending that you do not use ALCTYPE=KB or MB.   There is no MVS JCL equivalent to KB or MB when allocating in blocks so using KB or MB just adds additional confusion.


    The ALCTYPE=KB or MB option has been in the product for quite a long time, and as such, it will remain in the product.   It could be that some people think in terms of allocating in KB as they may have sized the data set in KB to start with.


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