Is it normal for old trends to be lost once the server on which it is running is restarted?
- Basic History?
- IM History?
- 800xA History?
Any diagnostic events in System Event list? Basic History often tell if a file is unreadable.
If a log file is lost, eg due to a CHKDSK Basic History will silently replace it with a new, empty one. File Creation time may be used to tell if a log file is new - object GUID is found in the name of each log file in Basic History.