Next: Disk Organisation
Up: No Title
Previous: Specifying permitted Users
There should be consistency maintained by the file system for all
users sharing the system :
Unix Semantics
- Writes performed by one user are immediately seen by other user(s)
- Can optionally share current location pointer :
User 1 reads block 510, User 2 then reads block 511 (Single File Image)
Session Semantics
- Writes to open file are not visible to other users
- When file closed, changes are made visible to new sessions, but are
not seen by current sessions
Multiple copies of files ?
Immutable Files
- Read only sharing - files cannot be changed
Locks
- Sharing of files
locking to give exclusive access
- Prevent others reading while the file is being updated
- Locks can be : On whole files or Individual record of a file
Omer F Rana
Sat Feb 15 19:06:41 GMT 1997