Chapter 6. Library Control; Determining The Size Of A Tape Or Diskette File - IBM 5110 User Manual

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DETERMINING THE SIZE OF A TAPE OR DISKETTE FILE
Before information can be stored on the media (tape or diskette), the
media files must be formatted by the )MARK command. When using
the )MARK command, you can use the following formulas to
determine the maximum size a file should be marked. The formula for
a workspace file [the contents of the active workspace were written to
the storage media with a )SAVE or )CONTINUE command] is MAXSIZE
=
r
3
+
(CLEAR-ACTIVE)
-+
1024, where:
• MAXSIZE is the maximum amount of media storage (number of
1024-byte blocks) that would be required to write the contents of
the active workspace to the media.
• CLEAR is the value of OWA in a clear workspace.
• ACTIVE is the value of OWA just before the contents of the active
workspace are written to the media.
The formula for a data file (data written to the media using an APL
shared variable) when all of the data is contained in the active
workspace is MAXSIZE
=
r
(WITHOUT-WITH)
-+
1024, where:
• MAXSIZE is the maximum amount of media storage (number of
1024·-byte blocks) required to write the data to the media.
• WITH is the value of OWA with the data in the active workspace.
• WITHOUT is the value of OW A before any data to be written to
tape or diskette was stored in the active workspace.
There is no formula for determining what size to mark a data file when
the data is written to the media as it is entered from the keyboard.
The amount of storage required depends upon how much data is
entered from the keyboard and what type of data is used. For
information on how many bytes of storage are required by the various
types of data, see Storage Considerations in the Active Workspace
Control chapter.