Technical data

Table 2–8: Link Files Differences
OpenVMS
UNIX
Files can exist without links. Files cannot exist without links.
Hard Links
OpenVMS systems allows you to perform a
function similar to hard links with the SET
FILE/ENTER and SET FILE/REMOVE
commands.
The OpenVMS operating system does not
maintain a count of links to a file. As a
result, you can delete a file without deleting
its links.
Hard Links
Hard links allow users to share the same
file under different pathnames. A hard link
cannot span file systems.
On UNIX systems, any changes to the file
are independent of the link used to refer
to the file. The UNIX system maintains a
count of the number of links to each file. If
removing a link results in the link count
becoming zero, the file is deleted. A file can
be deleted only by removing all of its links.
Symbolic Links
OpenVMS file systems do not support
symbolic links.
Symbolic Links
A symbolic link is a file that contains the
nameofthefiletowhichitisconnected.
Symbolic links provide a path to the original
file.
A UNIX symbolic link can span file systems.
Unlike a hard link, a symbolic link does not
maintain a link count. In addition, symbolic
links can exist after the file is deleted.
However, the system returns an error if the
symbolic link file is accessed after the file
it names is deleted.
2.2.9 File Structures
Table 2–9 describes the differences between the OpenVMS and UNIX file
structures.
Table 2–9: File Structure Differences
OpenVMS
UNIX
Supportsthreefilestructures:indexed,
relative, and sequential. OpenVMS also
supports the following record formats and
record attributes:
• Fixed length
• Variable length
• Variable with fixed-length control (VFC)
• Stream (including STREAM_LF and
STREAM_CR)
• Undefined
• Carriage return/carriage control
• Fortran carriage control
• VFC carriage control
Supports byte streams only.
The records in UNIX text files have the
same format as the OpenVMS Record
Management Services (RMS) STREAM_LF
record format.
2.2.10 File Ownership
The OpenVMS and UNIX operating systems use different mechanisms for file
ownership. Table 2–10 describes those differences.
2–8 Understanding OpenVMS and UNIX Implementations