11.01.2013 Views

ABCs of z/OS System Programming Volume 3 - IBM Redbooks

ABCs of z/OS System Programming Volume 3 - IBM Redbooks

ABCs of z/OS System Programming Volume 3 - IBM Redbooks

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

sets (see Figure 5-27 on page 287). In the DFSMS environment, you control volume selection<br />

through the storage class and storage group definitions you create, and by ACS routines. This<br />

means that users do not have to specify volume serial numbers with the VOL=SER<br />

parameter, or code a specific device type with the UNIT= parameter on their JCL. Due to a<br />

large number <strong>of</strong> volumes in one installation, the volume selection SMS routine can take a long<br />

time. A fast volume selection routine, which improves the best-fit and not-best-fit algorithms,<br />

is introduced in z/<strong>OS</strong> 1.8.<br />

When converting data sets for use in DFSMS, users do not have to remove these parameters<br />

from existing JCL because volume and unit information can be ignored with ACS routines.<br />

(However, you should work with users to evaluate UNIT and VOL=SER dependencies before<br />

conversion).<br />

If you keep the VOL=SER parameter for a non-SMS volume, but you are trying to access a<br />

system-managed data set, then SMS might not find the data set. All SMS data sets (the ones<br />

with a storage class) must reside on a system-managed volume.<br />

288 <strong>ABCs</strong> <strong>of</strong> z/<strong>OS</strong> <strong>System</strong> <strong>Programming</strong> <strong>Volume</strong> 3

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!