If you are issuing a FILEDEF for a DOS file, note that the OS prograa that will use the DOS file must have a DCB for it. For "ddna.e" in the
FILEDEF command line, use the ddname in that DCB. With the DSJ operand,
enter the file-id of the DOS file. Sometimes, CMS issues the FILEDEF command for you. Although the ces MOVEFILE command, the supported CMS program product interfaces, and the CMS OPEN routine each a default FILEDEF, you should issue the
FILEDEF command yourself to ensure the appropriate file is defined.
After you have issued the ACCESS and FILEDEF commands for an CS sequential or partitioned data set or DOS sequential file, CBS coa.ands (such as ASSEMBLE and STATE) can refer to the OS data set or DOS file
just as if it were a CMS file. Several other CMS commands can be used with OS data sets and Des
files that do not reside on CMS disks. See the Rgfgrgngg for a complete description of the CMS ACCESS, FILEDE', LISTDS, MOVEFILE, QUERY, RELEASE, and STATE commands.
For restrictions on reading OS data sets and tos files under CBS. see
the Ela1!ni1!g ang 2:ystg! Gu.!Qg. The CMS FILEDEF command allows you to specify the I/O device and the
file characteristics to be used by a prograa at execution ti.e. In
conjunction with the OS simulation scheme, FILEDEF siaulates the
functions of the data definition JCL statement.
FILEDEF may be used only with programs using OS macros and functions.
For example:
filedef file1 disk proga data a1
After issuing this command, your program referring to FILE1 would access PROGA DATA on your A-disk.
If you wished to supply data from your terminal for FILE1, you could
issue the command:
filedef file1 terminal
and enter the data for your program without recoapiling.
fi tapein tap2 (recfm fb lrecl 50 block 100 9track den 800) After issuing this command, programs referring to TAPEIN will access a
tape at virtual address 182. (Each tape unit in the eMS environaent bas
a symbolic name associated with it.) The tape must have been previously attached to the virtual machine by the VM/370 operator.
The AUXPROC option can only be used by a program call to FILEDEF and not
from the terminal. The CMS language interface prograas use this feature
for special I/O handling of certain (utility) data sets.
282 IBM VM/370 System Programmer's Guide

The AUXPROC option, followed by a fullword address of an auxiliary
processing routine, allows that routine to receive control from DMSSEE before any device I/O is performed. At the of its processing.
the auxiliary routine returns control to DMSSEB signaling whether or not I/O bas been performed. If it has not been done, DMSSEB performs the
appropriate device I/O. When control is received from DMSSEB, the general-purpose registers
contain the following information: GPR2 Data Control Block (DCB) address GPR3 = Base register for DMSSEB GPR8 = CMS OPSECT address GPR11 File Control Block (FCB) address GPR14 Return address in DMSSEB GPR15 Auxiliary processing routine address
all other registers = Work registers
The auxiliary processing routine must provide a save area in which to
save the general registers; this routine must also perform the save
operation. DMSSEB does not provide the address of a save area in
general register 13, as is usually the case. When control returns to DMSSEB, the general registers must be restored to their original values.
Control is returned to DMSSEB by branching to the address contained in
general register 14. GPR15 is used by the auxiliary processing routine to inform to DMSSEE of the action that has been or should be taken with the data block as
follows: Action GPR15=O No I/O performed by AUXPROC routine; DMSSEB will perform I/O. GPR1S(O GPR15>O I/O performed by AUXPROC routine and error was encountered. DMSSEB will take error action. I/O performed by AUXPROC routine with residual count in GPR15; DMSSEB returns normally. GPR15=64K I/O performed by AUXPROC routine with zero residual count. Part 3. Conversational Monitor system (CMS) 283