CA Dynam for VSE User Guide

Operator Device Switching Facility
Requirements
For operator switching to be active:
• The FISWTCH option of the DYNAM/FI option record must be specified at
installation time. For more information, see the DYNAM/FI option record in
the Programming Guide.
• There must be full Catalog support (CATALOG(YES) in the DYNAM/FI
option record).
• Each file for which switching is to be permissible must be defined in the
Catalog with DYNAMFI(YES) and with a device type of FI instead of either
TAPE or DISK. (See the description of DYNCAT.)
• The Catalog entry must contain all information to create either a tape or
disk file. This includes all options that affect CA Dynam/D, CA Dynam/T,
and CA Dynam/FI.
Operation
The device type selected by CA Dynam/FI is, as always, determined by the
label type (TLBL or DLBL). If, when presented with a tape mount message or
DASD space recovery options, the operator specifies a switch to the other
device type by responding DISK or TAPE, respectively. CA Dynam/FI will do
the following:
• Replace the existing TLBL or DLBL with a label record of the opposite type.
• Reinitiate the OPEN request.
Since the replacement label record has only the minimal required information,
the Catalog record must have all disk allocation values as well as all tape
options. In effect, all files eligible for switching must be completely catalogdriven.
DEFALLOC may be used in the absence of disk allocation values.
When switched files are processed as input, CA Dynam/FI recognizes that
switching has been done and, if necessary, overrides the TLBL or DLBL
statement in the job stream so the file may be accessed properly. In this case,
all data needed to process the file is recorded in the Catalog when the file is
created.
If a data file is defined as a generation data set, it is permissible for different
generations to reside on different device types. Again, the Catalog has all the
information needed for proper processing of any specified generation.
Chapter 6: Controlling File Independence 6–35