PRB: Block Size Must Be Set Before Doing Tape I/O (165274)
The information in this article applies to:
- Microsoft Win32 Application Programming Interface (API), when used with:
- the operating system: Microsoft Windows NT 3.51
- the operating system: Microsoft Windows NT 4.0
- the operating system: Microsoft Windows 2000
- the operating system: Microsoft Windows XP
This article was previously published under Q165274 SYMPTOMS
After you boot the system, Tape I/O functions fail and GetLastError returns
87L (ERROR_INVALID_PARAMETER). The same code begins to work after you run
NTBackup or another tape backup program.
CAUSE
This behavior is by design. When you start the system, the tape drivers are
not initialized with a value for the tape media block size. Until the
system is properly initialized with this information, all tape I/O fails as
described above.
RESOLUTION
Once the tape block size is either retrieved or set, then the system allows
tape I/O operations to proceed normally. Please note that other conditions
may still cause I/O operations to fail.
To avoid this problem, call the SetTapeParameters function to set the MEDIA
information or call the GetTapeParameters function to get the MEDIA
information. These operations cause the block size to be communicated to
the parts of the system that require it.
A well-written program should always set or get the tape block size before
issuing tape I/O operations. Programs doing this during initialization will
never see the error described above. Getting or setting the tape block size
is recommended because this allows a program to allocate I/O buffers with
sizes that are multiples of the block size. I/O operations with a buffer
size not a multiple of the tape block size will fail as described above.
In Windows NT 3.51, if GetTapeParameters is used to get DRIVE information,
the tape block size is propagated to the other parts of the system. Other
Windows NT versions require that the MEDIA information be set or retrieved
in order to propagate the block size to the other parts of the system.
MORE INFORMATION
This setting is system-wide. Programs may operate successfully without
explicitly getting or setting the tape block size if some other program
(for example, NTBackup) retrieves or sets the block size first.
| Modification Type: | Major | Last Reviewed: | 3/16/2004 |
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| Keywords: | kbAPI kbBackUp kbKernBase kbprb KB165274 |
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