IBM OS/390 User Manual

Figure 43. Record Reference by KEY i n VSE and MVS

Relative Track
Addressing

Assumed if DSKXTNT is
specified. RELTYPE=HEX
(the default) requires the
hexadecimal form TTTR.
RELTYPE=DEC requires the
zoned decimal form
TTITTTTTRR. RR must be 00.

Assumed if OPTCD does not
contain A. The field specified
by blockaddress must contain
TT in binary. There is no
equivalent to RELTYPE=DEC
in MVS. The form must be
converted to hexadecimal.

Relative Block
Addressing

No equivalent.

OPTCD=R must be specified
in the DCB parameter. The
field specified by block-
address must contain BB in
binary. The address of the
first record is 000.

Actual Physical
Addressing

Assumed if DSKXTNT is not
specified. The address must
be in the form MBBCCHHR.
The R must be 0. The field
specified by KEYARG must
contain the key of the record.

Assumed if OPTCD contains
an A. The field specified by
blockaddress must contain
MBBCCHHR. The M byte is
different in VSE and MVS.
See the description of the M
byte under Track and Record
Addressing.

In VSE, parameters required for creating or processing a DAM file are supplied
or made known through the DTFDA macro instruction operands and using the
READ/WRITE macros. For MVS, this information is in the DSCB, DCB, and
READ/WRITE macros. Some information is also supplied in optional fields of the
DD statement.

Figure 44, Figure 45 on page 319, Figure 46 on page 319, Figure 47 on
page 320, Figure 51 on page 325, Figure 48 on page 320, Figure 49 on
page 321 and Figure 50 on page 324 show parts of VSE programs with their
MVS counterparts for loading and processing DAM files.

OPEN

(DAMFILE,(UPDAT))

.
.

READ

DECBUPOT,DI,,,,OLDKEY,,MF=E

CHECK

DECBUPDT

.
.

READ

DECBUPDT,DI,DAMFILE,

′

S

′ , ′

S

′ , ,

C

BLOCKADDR,MF=L

.
.

DAMFILE

DCB

...DSORG=DA,MACRF=(RISC,WIC),

C

...OPTCD=R,BUFL=58...

.
.

Figure 44. Updating a D A M File u n d e r MVS

VSE to OS/390 Migration Workbook