IBM OS/390 User Manual

OPEN

(DAMFILE,(OUTPUT))

.
.

WRITE

DECBADD,DI,DAMFILE,DATA,

′

S

′ ,

KEY,BLOCKADDRESS

CHECK

DECBADD

.
.

DAMFILE

DCB

..MACRF=(WICS),DSORG=DA,OPTCD=R...

.
.

Figure 45. Adding to a D A M File u n d e r MVS

Figure 46 and Figure 47 on page 320 illustrate an example of sequentially
loading a DAM file consisting of fixed-length records with keys. A direct
addressing technique is used, which provides unique correspondence between
each key and its relative or actual position on the disk (VSE) or within the data
set (MVS), similar to a sequential data set. The input file resides on tape and is a
set of records sorted into ascending order by keys. Each record consists of 50
bytes (a three-byte key field followed by 47 bytes of data).

OPEN

DAMFILE,TAPE

WRITER0

WRITE DAMFILE,RZERO
WAITF DAFMFILE

.

GET

GET

TAPE

.

WRITE DAMFILE,AFTER
WAITF DAMFILE

.

EOF

WRITE DAMFILE,AFTER,EOF
WAITF DAMFILE
CLOSE DAMFILE,TAPE

.

DAMFILE

DTFDA BLKSIZE=58,ERRBYTE=ERROR,

C

IOAREA1=OUTPUT,SEEKADDR=ADDR,

C

TYPEFLE=OUTPUT,AFTER=YES,

C

DSKXTNT=3,KEYLEN=3,RELTYPE=HEX,

C

VERIFY=YES,DEVICE=3340

DAMOD AFTER=YES,ERREXT=YES,RELTRK=YES

.

TAPE

DTFMT .....
MTMOD

Figure 46. Loading a Sequential D A M File u n d e r VSE

The VSE program writes the capacity record (R0) and uses WRITE AFTER to
sequentially write each record, so that the capacity record is checked for
available space on that track before each record is written. In VSE, the total
amount of space allocated to the file is indicated by the extents allocated to it,
but it can be extended in a later run.

Chapter 13. A s s e m b l e r