>> If the dataset is SMS managed, the second volume won't allocate until you >> fill up the first volume and a second volume is needed. Why is it that you >> want to allocate the 2 volumes?
As someone stated earlier - a primary allocation can not span 2 volumes (for the most part). However, you can have a primary allocation on 2 volumes - of course, they're not mentioning that with the JCL you were given, you will also get 2ndary allocations on the 1st volume until you run out of either allowed extents on that volume or space on the volume and then would get the 2nd primary & more 2ndary allocations. That's a pretty simplified view and can be affected by the size of the volumes your shop is using, the way your dataclas is defined, etc. With that said, you Can get the primaries allocated on both volumes at initial allocation time - if the storage class your dataset is assigned is defined with the "Guaranteed Space" attribute. I'd have to hit the manuals to know for sure whether it writes to the 1st primary, then the 2nd primary, then 2ndary allocations on 1st volume, etc. or if you'll use all the primary & 2ndary space on the 1st volume before using the second. Another way to get your space allocated across multiple volumes would be by striping which is controlled by the "Init Acc Response" attribute of the storage class. This would would cause your primary allocation to split across a # of volumes to get you the desired intial access response time. When you write the DS out, you would send a write to the 1st volume, the 2nd write goes to the 2nd volume & so on. There are limitiation to this - IIRC you can only have 16 extents to a stripe. These are both kind of old fashioned now days & I'm sure that someone with a lot more time and energy than me can hit the manuals and pick all my thee's & thou's apart - I don't care & the reason I don't care is that you really need to have this discussion with your storage administration staff or whoever performs that function. They should understand the SMS environment and how it interacts with the hardware your shop has available. They need to have a clear understanding of what your needs really are before they can tell you the best way to go. For most applications, the primary allocation on the 1st volume, plus it's 2ndaries, then the primary on the 2nd volume and so on is both the most straight forward method and adequate for most application's needs. If your application has some very specific requirements, you need to have that discussion as SMS is generally controls your allocations through the rules & definitions they've set up. Hope that helps - dd keller This e-mail message and all attachments transmitted with it may contain legally privileged and/or confidential information intended solely for the use of the addressee(s). If the reader of this message is not the intended recipient, you are hereby notified that any reading, dissemination, distribution, copying, forwarding or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately and delete this message and all copies and backups thereof. Thank you. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
