Ron Hawkins wrote: Use a guaranteed space storage class, and specify a unit count in the JCL - e.g. UNIT=(,5). Specify a VOLSER list if you want the chunks in a particular volume order. This will allocate the primary extent requested on each of five volumes. When you write to it sequentially the five primary extents will fill before taking secondary extents on the fifth volume.
In short, you are advising me to use only primary allocation. That would work, all right, for the purpose of using max size allocation on each volume, when needed. I still have the problem of releasing unused space if any not on the last-used volume (I don't know in advance what space the file will need, this is a pre-defined parameter in the application). (in the above example, say I use 3 primary extents and a half, RLSE will free unused space on the 4th, but the 5th will stay allocated). Thank you for your input anyway, and thanks to all who took the time to answer (and fast, at that ...) > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] > On Behalf Of DEBERT Jean-Louis > Sent: Tuesday, November 06, 2012 5:15 AM > To: [email protected] > Subject: [IBM-MAIN] multi-volume SMS file allocation > > Hello list, > > Does anybody know if/how it is possible to force SMS to allocate > extents (the > primary allocation then each secondary allocation) on different > volumes (even if there is space enough on the first volume to put > several extents > there) ? > > This would be for an application that writes the file sequentially > (for > performance) but then will read it direct access, using FEOV and POINT (with > as many DCB's as there are different volumes). > You guessed it, the application uses BSAM READ/WRITE with > (respectively) POINT/NOTE with TTR. > > The multi-volume data set is one way to somewhat allow more space than > TTR addressing allows (65,535 tracks on any volume) and for this > purpose, it is > best to have (ideally) the largest possible allocation, but no more, > on each > volume. > The same would be true if using TTTR (although with a bigger > addressable space per volume) > > Any hints are welcome. > > Thanks in advance. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send > email to > [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
