从Oracle数据库9i开始，Oracle的外部表技术（Oracle External Tables）得到了极大的完善，通过外部表访问外部数据增强了Oracle和外部数据源进行数据交互的能力，对于数据仓库和ETL来说，这些增强都极大的方便了数据的访问。
对于数据库管理员（DBA）而言，在此前提下，可以很方便的使用外部表来访问警告日志文件或其它跟踪文件.
下文中的示例将详细说明外部表的具体用途：
首先，我们需要创建一个Directory：
[oracle@jumper oracle]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Sun Oct 15 21:42:28 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production
SQL> create or replace directory bdump
2 as '/opt/oracle/admin/eygle/bdump';
Directory created.
SQL> col DIRECTORY_PATH for a30
SQL> col owner for a10
SQL> select * from dba_directories;
OWNER DIRECTORY_NAME DIRECTORY_PATH
---------- ------- ----------------
SYS BDUMP /opt/oracle/admin/eygle/bdump
然后需要创建一个外部表:
SQL> create table alert_log ( text varchar2(400) )
2 organization external (
3 type oracle_loader
4 default directory BDUMP
5 access parameters (
6 records delimited by newline
7 nobadfile
8 nodiscardfile
9 nologfile
10 )
11 location('alert_eygle.log')
12 )
13 reject limit unlimited
14 /
Table created.
然后我们就可以通过外部表进行查询警告日志的内容:
SQL> select * from alert_log where rownum < 51;
TEXT
---------------------------------------------------
Mon Jun 26 12:00:24 2006
Starting ORACLE instance (normal)
Mon Jun 26 12:00:25 2006
WARNING: EINVAL creating segment of size 0x0000000008c00000
fix shm parameters in /etc/system or equivalent
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
SCN scheme 2
Using log_archive_dest parameter default value
LICENSE_MAX_USERS = 0
SYS auditing is disabled
Starting up ORACLE RDBMS Version: 9.2.0.4.0.
System parameters with non-default values:
processes = 150
timed_statistics = TRUE
shared_pool_size = 104857600
large_pool_size = 0
java_pool_size = 0
control_files = /opt/oracle/oradata/eygle/control01.ctl
db_block_size = 8192
db_cache_size = 16777216
db_cache_advice = ON
compatible = 9.2.0.0.0
db_file_multiblock_read_count= 16
fast_start_mttr_target = 300
log_checkpoints_to_alert = TRUE
undo_management = AUTO
undo_tablespace = UNDOTBS1
undo_retention = 10800
remote_login_passwordfile= EXCLUSIVE
db_domain =
instance_name = eygle
job_queue_processes = 10
hash_join_enabled = TRUE
background_dump_dest = /opt/oracle/admin/eygle/bdump
user_dump_dest = /opt/oracle/admin/eygle/udump
core_dump_dest = /opt/oracle/admin/eygle/cdump
sort_area_size = 524288
db_name = eygle
open_cursors = 500
star_transformation_enabled= FALSE
query_rewrite_enabled = FALSE
pga_aggregate_target = 52428800
aq_tm_processes = 0
PMON started with pid=2
DBW0 started with pid=3
LGWR started with pid=4
CKPT started with pid=5
SMON started with pid=6
RECO started with pid=7
50 rows selected.
SQL>
假如需要查看数据库中曾经出现过的ORA-错误，可以执行下面的查询:
SQL> select * from alert_log where text like 'ORA-%';
TEXT
-----------------------------------------------------
ORA-1652: unable to extend temp segment by 128 in tablespace TEMP
ORA-1113 signalled during: alter database open...
ORA-1113 signalled during: alter database datafile 3 online...
ORA-09968: scumnt: unable to lock file
ORA-1102 signalled during: ALTER DATABASE MOUNT...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/users01.dbf'
ORA-27037: unable to obtain file status
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/users01.dbf'
TEXT
-----------------------------------------------------
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-27037: unable to obtain file status
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-27037: unable to obtain file status
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
TEXT
---------------------------------------------------
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1113 signalled during: alter database open...
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-27037: unable to obtain file status
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-1113 signalled during: alter database open...
ORA-1122 signalled during: alter database open...
ORA-283 signalled during: ALTER DATABASE RECOVER database ...
ORA-1122 signalled during: alter database open...
TEXT
------------------------------------------------
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1113 signalled during: ALTER DATABASE OPEN...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1122 signalled during: ALTER DATABASE OPEN...
ORA-1503 signalled during: CREATE CONTROLFILE REUSE DATABASE "EYGLE" NORESETL...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1991 signalled during: ALTER DATABASE MOUNT...
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-01115: IO error reading block from file 4 (block # 1)
ORA-27069: skgfdisp: attempt to do I/O beyond the range of the file
ORA-01122: database file 1 failed verification check
TEXT
----------------------------------------------------
ORA-01110: data file 1: '/opt/oracle/oradata/eygle/system01.dbf'
ORA-01207: file is more recent than controlfile - old controlfile
ORA-1122 signalled during: alter database open...
ORA-283 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-01115: IO error reading block from file 4 (block # 1)
ORA-27069: skgfdisp: attempt to do I/O beyond the range of the file
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/opt/oracle/oradata/eygle/system01.dbf'
ORA-1194 signalled during: alter database open resetlogs...
ORA-283 signalled during: ALTER DATABASE RECOVER datafile 1 ...
TEXT
----------------------------------------------------
ORA-283 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
ORA-01115: IO error reading block from file 4 (block # 1)
ORA-27069: skgfdisp: attempt to do I/O beyond the range of the file
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/opt/oracle/oradata/eygle/system01.dbf'
ORA-1194 signalled during: alter database open resetlogs...
ORA-283 signalled during: ALTER DATABASE RECOVER datafile 1 ...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1589 signalled during: ALTER DATABASE OPEN...
ORA-01110: data file 4: '/opt/oracle/oradata/eygle/eygle01.dbf'
TEXT
---------------------------------------------------
ORA-01115: IO error reading block from file 4 (block # 1)
ORA-27069: skgfdisp: attempt to do I/O beyond the range of the file
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/opt/oracle/oradata/eygle/system01.dbf'
ORA-1194 signalled during: alter database open resetlogs...
ORA-1109 signalled during: alter database close...
ORA-1503 signalled during: CREATE CONTROLFILE REUSE DATABASE "EYGLE" NORESETL...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1113 signalled during: alter database open...
ORA-00202: controlfile: '/opt/oracle/oradata/eygle/control01.ctl'
ORA-27037: unable to obtain file status
TEXT
------------------------------------------------
ORA-205 signalled during: ALTER DATABASE MOUNT...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-01501: CREATE DATABASE failed
ORA-01526: error in opening file '?/rdbms/admin/sql.bsq'
ORA-07391: sftopn: fopen error
ORA-01526: error in opening file ''
ORA-1092 signalled during: CREATE DATABASE eygle
ORA-1079 signalled during: ALTER DATABASE MOUNT...
ORA-1507 signalled during: alter database open...
ORA-214 signalled during: alter database mount...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
TEXT
-----------------------------------------------
ORA-214 signalled during: ALTER DATABASE MOUNT...
ORA-214 signalled during: alter database mount...
ORA-1113 signalled during: ALTER DATABASE OPEN...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
ORA-27037: unable to obtain file status
ORA-1113 signalled during: ALTER DATABASE OPEN...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
ORA-27037: unable to obtain file status
ORA-1113 signalled during: alter database open...
TEXT
------------------------------------------------------
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
ORA-27037: unable to obtain file status
ORA-283 signalled during: ALTER DATABASE RECOVER database ...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1100 signalled during: alter database mount...
ORA-1178 signalled during: alter database create datafile '/opt/oracle/produc...
ORA-1516 signalled during: alter database create datafile '/opt/oracle/oradat...
ORA-1991 signalled during: ALTER DATABASE MOUNT...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
TEXT
------------------------------------------------------
ORA-27037: unable to obtain file status
ORA-283 signalled during: ALTER DATABASE RECOVER database ...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
ORA-27037: unable to obtain file status
ORA-283 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1991 signalled during: ALTER DATABASE MOUNT...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/users01.dbf'
ORA-27037: unable to obtain file status
TEXT
------------------------------------------------------
ORA-283 signalled during: ALTER DATABASE RECOVER database ...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/users01.dbf'
ORA-27037: unable to obtain file status
ORA-283 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/users01.dbf'
ORA-27037: unable to obtain file status
ORA-283 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-279 signalled during: ALTER DATABASE RECOVER database using backup cont...
ORA-308 signalled during: ALTER DATABASE RECOVER CONTINUE DEFAULT ...
TEXT
-------------------------------------------------
ORA-308 signalled during: ALTER DATABASE RECOVER CONTINUE DEFAULT ...
ORA-1547 signalled during: ALTER DATABASE RECOVER CANCEL ...
ORA-1589 signalled during: alter database open...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1503 signalled during: CREATE CONTROLFILE REUSE DATABASE "EYGLE" NORESETL...
ORA-1178 signalled during: alter database create datafile '/opt/oracle/produc...
ORA-1991 signalled during: ALTER DATABASE MOUNT...
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'
ORA-27037: unable to obtain file status
ORA-1157 signalled during: alter database open...
TEXT
--------------------------------------------------
ORA-1113 signalled during: alter database open...
ORA-1991 signalled during: ALTER DATABASE MOUNT...
ORA-1109 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1031 signalled during: alter database open...
ORA-3217 signalled during: ALTER TABLESPACE TEMP DEFAULT STORAGE (INITIAL 10M...
ORA-1507 signalled during: alter database close...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1507 signalled during: alter database close normal...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1106 signalled during: alter database dismount...
ORA-1531 signalled during: alter database open...
TEXT
-------------------------------------------------
ORA-1531 signalled during: alter database open...
ORA-1531 signalled during: alter database open...
ORA-1531 signalled during: alter database open...
ORA-1531 signalled during: alter database open...
ORA-1109 signalled during: alter database close...
ORA-1507 signalled during: alter database close...
ORA-1507 signalled during: ALTER DATABASE CLOSE NORMAL...
ORA-1185 signalled during: alter database add logfile group 6
ORA-350 signalled during: alter database drop logfile group 3...
163 rows selected.
SQL>
