SQL> select ORIGINATING_TIMESTAMP, MESSAGE_TEXT from V$DIAG_ALERT_EXT where MESSAGE_TEXT like '%ORA-%';

ORIGINATING_TIMESTAMP
---------------------------------------------------------------------------
MESSAGE_TEXT
-------------------------------------------------------------------------------------------------------------
31-JAN-12 01.12.39.441000000 PM +01:00
ORA-7452: resource plan 'SYSTEM_PLAN' does not exist

29-FEB-12 10.15.06.391000000 PM +01:00
Errors in file C:\ORACLE\ADMIN\MIKB2\TRACE\diag\rdbms\mikb2\mikb2\trace\mikb2_j002_2580.trc:
ORA-16957: SQL Analyze time limit interrupt

10-JUN-12 01.46.20.771000000 PM +02:00
Non critical error ORA-48913 caught while writing to trace file "C:\ORACLE\ADMIN\MIKB2\TRACE\diag\rdbms\mikb2
e\mikb2_dbrm_844.trc"
Error message: ORA-48913: Writing into trace file failed, file size limit [5242880] reached
Writing to the above trace file is disabled for now on...

29-JUN-12 11.33.39.818000000 AM +02:00
Errors in file C:\ORACLE\ADMIN\MIKB2\TRACE\diag\rdbms\mikb2\mikb2\trace\mikb2_ora_5304.trc  (incident=68193):
ORA-00600: internal error code, arguments: [4353], [U], [0], [94], [], [], [], [], [], [], [], []

29-JUN-12 11.33.52.318000000 AM +02:00
Errors in file C:\ORACLE\ADMIN\MIKB2\TRACE\diag\rdbms\mikb2\mikb2\trace\mikb2_ora_5304.trc  (incident=68194):
ORA-00603: ORACLE server session terminated by fatal error
ORA-00600: internal error code, arguments: [4353], [U], [0], [94], [], [], [], [], [], [], [], []

29-JUN-12 11.33.53.630000000 AM +02:00
opiodr aborting process unknown ospid (5304) as a result of ORA-603

SQL> create or replace directory BDUMP_DIR as 'C:\ORACLE\ADMIN\MIKA\BDUMP';

Directory created.

SQL> drop table alert_log_ext;

Table dropped.

SQL> create table alert_log_ext (line varchar2(2000))
  2  organization external (
  3     type oracle_loader
  4     default directory bdump_dir
  5     access parameters (
  6        records delimited by newline
  7        nobadfile
  8        nologfile
  9        nodiscardfile
 10        fields
 11        missing field values are null
 12        (line position (1:2000))
 13        )
 14     location ('alert_mika.log') 
 15     )
 16  reject limit unlimited
 17  /

Table created.

SQL> select line from alert_log_ext where line like '%ORA-%' and rownum <= 10;
LINE
----------------------------------------------------------------------------------------------------
ORA-07445: exception encountered: core dump [ACCESS_VIOLATION] [unable_to_trans_pc] [PC:0x7C911689]
[ADDR:0x0] [UNABLE_TO_READ] []
ORA-07445: exception encountered: core dump [ACCESS_VIOLATION] [unable_to_trans_pc] [PC:0x7C9101B3]
[ADDR:0x52005A] [UNABLE_TO_WRITE] []
ORA-07445: exception encountered: core dump [ACCESS_VIOLATION] [unable_to_trans_pc] [PC:0x7C911780]
[ADDR:0x8A01C083] [UNABLE_TO_READ] []
ORA-00472: PMON  process terminated with error
ORA-00472: PMON  process terminated with error
ORA-00472: PMON  process terminated with error
ORA-00472: PMON  process terminated with error
ORA-19815: WARNING: db_recovery_file_dest_size of 1073741824 bytes is 92.30% used, and has 82706432
remaining bytes available.
ORA-07445: exception encountered: core dump [ACCESS_VIOLATION] [unable_to_trans_pc] [PC:0x7C911689]
[ADDR:0x0] [UNABLE_TO_READ] []
ORA-19815: WARNING: db_recovery_file_dest_size of 1073741824 bytes is 92.30% used, and has 82706432
remaining bytes available.

10 rows selected.

SQL> grant select on x$dbgalertext to testuser;
grant select on x$dbgalertext to testuser
                *
ERROR at line 1:
ORA-02030: can only select from fixed tables/views