IBM OS/390 manual Open DAMFILE,OUTPUT, Decbadd, Damfile DCB MACRF=WICS,DSORG=DA,OPTCD=R

OPEN	(DAMFILE,(OUTPUT))
.
.	DECBADD,DI,DAMFILE,DATA,′ S′ , KEY,BLOCKADDRESS
WRITE
CHECK	DECBADD
.
.
DAMFILE DCB	..MACRF=(WICS),DSORG=DA,OPTCD=R...
.
.

Figure 45. Adding to a DAM File under MVS

Loading a DAM File (Fixed-Length Records with keys)

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 DAM File under 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 319