To dump all the datafile headers use
ALTER SESSION SET EVENTS 'immediate trace name file_hdrs level level';
Levels (circa Oracle 8.1.5) are:
| Level | Description |
| 1 | Dump datafile entry from control file |
| 2 | Level 1 + generic file header |
| 3 | Level 2 + datafile header |
| 10 | Same as level 3 |
In later versions, level 7 appears to generate additional trace.
The following ORADEBUG command has the same effect:
ORADEBUG DUMP FILE_HDRS level