The system attempts to extend to another DASD volume if all of
the following conditions exist:
The
current volume does not have the secondary space amount available,
or the data set reached the extent limit for that type of data set,
or the application program issued the FEOV macro.
The volume count has not yet been reached. For a system-managed
data set, the volume count was determined when the data set was created
(DISP=NEW) and is the largest of the volume count (VOL=(,,,nn)),
the number of volumes coded with the VOL parameter, and the unit count
(UNIT=(xxxx,nn)).
For
either system-managed or non-system-managed data sets, the volume
count can come from the data class. The volume count can be increased
after data set creation with the IDCAMS ADDVOL command.
The dynamic volume count has not
been reached for a system-managed data set. You can define the Space
Constraint Relief and Dynamic Volume Count attributes in the data
class. If Space Constraint Relief=YES, you can specify a dynamic volume
count from 1 to 59 for SMS to extend a data set automatically to another
volume or volumes. For more information, see z/OS DFSMSdfp Storage Administration.
A secondary allocation amount is available. This can come from
the data class when the data set was created even if the data set
is not system managed. When the data set is created with DISP=NEW
or IDCAMS DEFINE, the secondary amount permanently overrides data
class for the data set. For a non-VSAM data set the preceding two
sources of the secondary amount can be overridden temporarily with
DISP other than NEW.
Note: After a multivolume
data set is unable to extend on the current volume and the data set
is extended to a new volume, then all previous volumes can no longer
be selected for future extensions.