If the disk you want to access replaces an OS disk, message DMSACC724I appears at your terminal.
If you specified any options or fileid in the ACCESS command to an OS disk, a warning message, DMSACC230W, appears to notify you that such
options or fileid were ignored. DMSACC returns to the calling routine
with a warning code of 4. DMSACF verifies that the disk you want to access is an OS disk and, if it is, exits immediately. DMSACM MODULE: DMSACM saves the disk label and VTOC address in the ADT block- Ii-the disk is an as disk. DMSACM checks to determine if a
previous access to an os disk leaded DMSROS. If not, DMSACM calls DMSSTT to verify that DMSROS text exists. Upon successful return from
STATE, DMSACM loads DMSROS text into the high storage area with the same
protect key and calls the OS access routine (ROSACC) of DMSROS to read
the format 4 DSCB of the disk. Upon successful return from DMSROS, control returns to the calling routine. Any other errors are treated as
general logen errors. DMSALU MODULE: If the disk is an os disk, DMSFRET returns the as FST blocks clf-any) to free storage. DMSALU clears the OS FST pointer in
all active as file control blocks, decrements the DMSROS usage count
and, if the usage count is zero, clears the address of DMSROS in the
nucleus area. DMSALU also calls DMSFRET to returns to free storage the
area which DMSROS occupies. DMSARE MODULE: DMSARE ensures that the disk you want to relase is an OS aisk:- -DMSliE calls DMSALU to release alIOS FST blocks and, if
necessary, to free the DMSROS occupies. UFon return from DMSALU, DMSARE clears the common CMS and OS active disk table. • DSN If you specify the parameter DSN as a question mark (1) ,
FILEDEF displays the message DMSFLD220R to request you to type in an OS data set name with the format Q1.Q2.QN. Ql, Q2, and QN are the
qualifiers of an OS data set name. If you specify the parameter DSN as Ql.Q2.QN, FILEDEF assumes that Ql, Q2, and QN are the qualifiers
of an OS data set name, and stores the qualifiers with the format Ql.Q2.QN in a free storage block and chains the block to the FCB. • CONCAT -- If you specify the CONCAT option, FILEDEF assumes that the
specified FILEDEF is unique unless a filedef is outstanding with a
matching ddna.e, filename, and filetype. This allows you to specify
more than one FILEDEF for a particular ddna.e. The CONCAT option
also sets the FCBCATML bit in the FCB to allow the OS simulation
routine to know the FCB is for a concatenated MACLI8. • MEMBER -- If you specify the member option, filedef stores the member
name in FCBMEMBR in the FCB to indicate that the OS simulation
routine should set the read/write pointer to point to the specified BPAM file member when OPEN occurs. DMSLDS saves the return register, sets itself with the
nucleus protection key, clears the dsname key, and initializes its
internal flag. DMSLDS verifies parameter list validity. The data set name must not
exceed 44 characters, and the disk mode (the last parameter before the
options) must be valid. DMSLDS joins the quailifiers with dots (.) to
form valid data set names. If you specify the data set name as a
question mark (?), DMSLDS prompts you to enter the dsname in exactly the
same form as the dsname which apFears on the disk.
2-132 IBM VM/370 System Logic and Program Determination--Volume 2

DMSLDS calls DMSLAD to find the active disk table block. If you
specify file mode as an asterisk (*), DMSLAD searches for all ADT blocks.
If you specify the filemode as alphabetic, DMSLAD finds only the AtT tlock for the specified filemode.
If you specify the dsname (which is optional), DMSLDS sets the
channel programs to read by key= If you did not specify a dsname, DMSLDS searches the whole VTOC for format 1 DSCES and displays all the
requested information contained in the DSCB on your console. If you
specify the format option, the RECFM, LRECL, ELKSI, DSCRG, DATE, LABEL, FMODE, and data set name appear on you console; otherwise, only the FMODE and data set name appear. If you specify the PDS option, DMSLDS calls the 'find' routine
(rosfind) in DMSROS to read the member directory and pass back, one at a
time, in the fcbmembr field of CMSCB the name of each member of the data
set. This occurs if the data set is partitioned.
After processing finishes, DMSLDS resets the nucleus key to the same
value as the user key, puts the return code in register 15, and returns
to the calling routine. DMSLFS verifies that the FST being searched for has an CS disk associated with it. DMSLFS calls the DMSROS state routine (ROSSTT) to verify that the data set exists and eMS supports the data set
attributes. Upon return from DMSROS, a return code of 88 indicates that
the data set was not found, and DMSLDS starts the search again using the
next disk in sequencee Any other errors, such as a return code 80, cause DMSLFS to exit immediately. A return code of 0 from DMSRCS indicates that the data set is on the specified disk. From this point
on, execution occurs common to both CMS and OS disks. DMSMVE MODULE: If you specify the PDS option and the input is from a aisk;-DMSMvi-sets the FCBMVPDS bit and issues an as FIND macro before
opening an output DCB to position the input file at the next DMSMVE then stores the input member name in the output CMSCB for use as
the output filename. After reaching end-of-file on a member, the
message DMSMVE225I appears, DMSMVEcloses the output DCB, and passes
control to find the next member. After moving all the members to
separate eMS files, movefile displays message DMSMVE226I, closes the
input and outFut DCBS, and returns control to the calling routine. • ROSACC Routine -- ROSACC gets control from DMSACft after DftS!CH determines that the label of the disk belongs to an as disk. The ROSACC routine reads the format 4 DSCB of the disk to further verify
the validity of the OS disk. ROSACC updates the ADT to contain the
address of the high extent of the VTOC (if the disk is a DOS disk) or
the address of the last active for.at 1 DSCE (if the disk is an CS disk), and the number of cylinders in the disk. If the disk is a Des
disk, ROSACC sets a flag in the ADT. Information messages appear to
notify you that the disk was accessed in read-only mode. If the disk
is already accessed as another disk, another information message
appears to that effect. Finally ROSACC zeroes out the ADTFLG1 flag
in the ADT, sets the ADRFLG2 flag to reflect that an OS disk was 3ccessed, and returns control to the calling routine.
• ROSSTT Routine --Verifies the existence of an CS data set and
verifies the support of the data set attributes. Within the ROSSTT description, any reference to FCB or CMSCB implies a DoseB if DOS is active. CMS Method of Operation and Program Organization 2-133