Oracle ORA-00600 [4000] ORA-600 [4000] “trying to get dba of undo segment header block from usn”

Bug 1362499
ORA-600 [4000] after migrating 7.3.4.3 to 8.0.6.1 on HP-UX 32-bit Specific to HP-UX, fixed in one-off patch

Historic info on the Oracle 7.3.x issues re unlimited extents and bootstrap$

In 7.3.4 then due to Bug:434596, this can result from altering the SYS.BOOTSTRAP$ table.

When a SHUTDOWN command follows this, the database will not startup again. Example: Any of following modifications of SYS.BOOTSTRAP$

will cause this error:
ALTER TABLE BOOTSTRAP$ STORAGE (MAXEXTENTS UNLIMITED ); ALTER TABLE BOOTSTRAP$ STORAGE (NEXT 1024);
ALTER TABLE SYS.BOOTSTRAP$ STORAGE (MAXEXTENTS UNLIMITED); ALTER TABLE sys.BOOTSTRAP$ STORAGE (MAXEXTENTS UNLIMITED);

A lock byte is now set on the SYS.BOOTSTRAP$ segment header and following shutdown the database will not start.

A select from bootstrap$ before shutdown will cleanout the lock on
the SYS.BOOTSTRAP$ segment header and prevent the errors from occuring. Example: Issue the following BEFORE shutdown:

sql> select count(*) from sys.bootstrap$;
Get a backup history of the Database/s and the exact sequence of steps performed. Two possible options
a) Go back to backup before the storage clause on BOOTSTRAP$ was changed

b) Oracle Support may be able to patch bootstrap$. See Note:43132.1

Obviously, option a) is always the way to go if at all possible.

Articles:
ALERT about changing MAXEXTENTS to UNLIMITED Note:50380.1

Another cause of an ORA-600 [4000] is that a block scn is ahead of the database scn. In that case the block with the high scn could be printed in the trace file and