1 01/24/84  Damaged Segments
 2 
 3 If a device error or system crash causes a page of a segment to be
 4 destroyed, the supervisor sets a special switch associated with the
 5 segment called the damaged switch.  An attempt to reference the
 6 contents of a segment whose damaged switch is on causes an error with
 7 the message:
 8 
 9     Entry has been damaged. Please type "help damaged_segments.gi".
10 
11 Two cases can occur.  Sometimes, the only valid copy of a page of the
12 segment was destroyed; if so, a page of zeroes appears in the segment.
13 In other, rare, cases, a modified page of a segment cannot be written
14 out due to a paging device error; when this occurs, the original
15 unmodifed page may be supplied.
16 
17 
18 When a damaged segment is detected, the owner of the segment should
19 change the ACL of the segment so that no other user can reference it,
20 and then reset the damaged switch using the switch_off command.  The
21 owner should then inspect the segment's contents to determine the
22 extent of the damage.  If the damage is easily correctable, the user
23 can simply fix the segment and continue.  Otherwise, the segment
24 should be retrieved from the last known good copy.