What does the error "Insufficient disk space or Write access denied" really mean ?

What does the error "Insufficient disk space or Write access denied" really mean?
Guidelines for troubleshooting error 291.
 

The Progress (291) error is:
A (291) error can be caused by insufficient disk space or can be caused by anything that prevents disk reads and writes such as:

• Physical read error or write error on the disk itself
• A network problem (if trying to access a disk on a network)
• A file permissions problem
• A file not shared properly and some other person or process has it locked up at this moment
• Not enough file handles (this is a common problem in UNIX, MS-DOS and Windows 3.1/3.11 but not in Windows 95/98 or NT).
• Hardware problem
• Insufficient disk space if the file to save is bigger than the space available (for example a big temporary sort file OR outputting results of a large report to a text file).

The (291) is a "pass through error message."  That is, all the text to the left of the (291) was generated by the Operating System and then delivered to Progress. Progress then displays the words from the Operating System and appends the "(291)" onto the right side of the error message. To find the true cause of the error message, look up the error text and operating system error number (if any) in the operating system's manuals.

Some steps to isolate the cause:

1. Enable clientlogging with logentrytype FileID to find which file the client or agent process is trying to access or write to.
2. Test the disk physically by copying, modifying and saving files. The test files should be the same size as those that were in use when the (291) error occurred.  This is also true if the disk is on the network.
3. .On Unix use ls -lisa on Windows use the Windows Explorer -> right click on the folder or file -> Properties -> Security -> Permissions to check thefile permissions
4. A file size of 0 indicates that the file is in use by an other user.
5. An Operating System error will occur if a file is attempted to be moved while the file is in use.
6. On UNIX use the command ulimit -Sa and ulimit -Ha to check available file handles.
7. On UNIX, empty /tmp by periodically rebooting or by using rm command to regularly remove unnecessary files from /tmp.
8. Use Operating System utilities to check the hardware e.g. chkdsk on Windows.
9. Use df on UNIX or on Windows use the Windows Explorer -> right click on the folder or file -> Properties -> General to check if there is enough disk space available for the temporary files.

Correct issues as encountered.