[[email protected] ~]$ vi /etc/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.
#
# 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.
#
#
orcl:/u01/app/oracle/product/10.2.0/db_1:N
最后的N或者Y表示是否允许dbstart来启动数据库，如果为N则实例不能通过dbstart启动，表现为sqlplus连接实例时显示Connected to an idle instance.如果为Y则实例可以通过dbstart启动，sqlplus连接后数据库即为open状态。
参考：http://blog.chinaunix.net/uid-23177306-id-2531086.html