A single-volume file is a file which is stored on a single tape (volume).
Structure of a single-volume file
The volume header label VOL1 is followed by the file header labels, which are separated from the first data block by a tape mark. The data blocks may have the standard format (PAM page: 2048 bytes; with or without a PAM key) or a nonstandard format (no PAM key, variable block size; see section "Block formats for tape files"). The end-of-file labels are also separated from the data blocks by a tape mark. The end of the tape is always indicated by a double tape mark.
Creating a single-volume file
In the FILE macro, the DEVICE and VOLUME operands define the device type for the volume and the volume itself. In the CREATE-FILE command this is done by means of the DEVICE-TYPE and VOLUME operands. An entry is made in the task file table by means of the LINK operand in the FILE macro or the LINK-NAME operand in the ADD-FILE-LINK command, as appropriate. The user can request a specific volume (VOLUME=vsn) or allow the system operator to allocate a volume (VOLUME=PRIVATE or VOLUME=*ANY). If the user makes no further entries for LABEL (or LABEL-TYPE) etc., a standard tape file is created, currently in accordance with DIN 66029, exchange level 3. In other words the file receives, by default, three HDR labels (HDR1-3) and three EOF labels (EOF1-3).
If the user wishes to use his/her own labels, he/she must define the appropriate label routines in the EXLST macro. The system branches automatically to these routines after it has written the preceding system labels.
With respect to all other file attributes which are defined by means of a macro or in the program (access method, record format, etc.), the rules for tape files are the same as for disk files, except that ISAM processing of tape files is not possible.