linux下手动删除数据库实例，直接删除相应的目录就可以了，不多说了....
1. $ORACLE_HOME/dbs/
[oracle9@frogger dbs]$ pwd
/u01/app/oracle/product/9.2.0.1/dbs
[oracle9@frogger dbs]$ rm inittest02.ora
[oracle9@frogger dbs]$ rm orapwdtest02
2. $ORACLE_BASE/oradata/SID
[oracle9@frogger oradata]$ ls
default_demo01.dbf default_demo99.dbf devdb02 duke1 test01 test01_bak test02 testdk testqa
[oracle9@frogger oradata]$ ps -ef|grep smon
oracle9 7162 1 0 2008 ? 00:04:30 ora_smon_duke
oracle9 3313 1 0 2008 ? 00:02:30 ora_smon_testdk
oracle9 4386 1 0 Apr05 ? 00:00:07 ora_smon_test01
oracle9 4620 1 0 Apr05 ? 00:00:05 ora_smon_dvdsame
oracle9 12307 4426 0 22:53 pts/3 00:00:00 grep smon
[oracle9@frogger oradata]$ rm -rf test02
[oracle9@frogger oradata]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
455G 381G 51G 89% /
/dev/sda1 99M 15M 80M 16% /boot
none 1004M 0 1004M 0% /dev/shm
nfs-vip.certificatesnow.com:/u07
455G 230G 202G 54% /u07
[oracle9@frogger oradata]$ ls
default_demo01.dbf default_demo99.dbf devdb02 duke1 test01 test01_bak testdk testqa
3. 删除log文件
[oracle9@frogger admin]$ ls
devdb02 duke1 test01 test02 testdk testqa
[oracle9@frogger admin]$ pwd
/u01/app/oracle/admin
[oracle9@frogger admin]$ cd test02
[oracle9@frogger test02]$ ls
bdump cdump create pfile udump
[oracle9@frogger test02]$ cd ..
[oracle9@frogger admin]$ ls
devdb02 duke1 test01 test02 testdk testqa
[oracle9@frogger admin]$ rm -rf test02
[oracle9@frogger admin]$ ls
devdb02 duke1 test01 testdk testqa
[oracle9@frogger admin]$
4. 如果是用dbca创建的实例，则还要删除/etc/oratab文件中的实例信息，就一行。 删除就ok了。
/etc/oratab 运行root.sh产生的,中每一行代表一个ORACLE 实例,不允许有相同的名字，对已经存在的数据库会提示是否升级等,安
装创建数据库的时候会去检查这个文件是否存在和并检查文件中的内容,在运行dbstart 时会检查这个文件，如果是Y就启动它，是N
就不管它。
[oracle9@frogger admin]$ cd /etc
[oracle9@frogger etc]$ more oratab
#
# This file is used by ORACLE utilities. It is created by root.sh
# and updated by the Database Configuration Assistant when creating
# a database.
# A colon, ':', is used as the field terminator. A new line terminates
# the entry. Lines beginning with a pound sign, '#', are comments.
#
# Entries are of the form:
# $ORACLE_SID:$ORACLE_HOME:<N|Y>:
#
# The first and second fields are the system identifier and home
# directory of the database respectively. The third filed indicates
# to the dbstart utility that the database should , "Y", or should not,
# "N", be brought up at system boot time.
#
# Multiple entries with the same $ORACLE_SID are not allowed.
#
#
# *:/u01/app/oracle/product/9.2.0.1:N
*:/u01/app/oracle/product/9.2.0.1:N
duke:/u01/app/oracle/product/9.2.0.1:N
test02:/u01/app/oracle/product/9.2.0.1:N
[oracle9@frogger etc]$