Oracle 12c R2 图形化升级时提示No databases detected

图像化12.1 升级12.2 时，页面提示No databases detected 如下图：

解决方法：

在/etc/oratab 文件中添加标红色的部分

[[email protected] ~]$ cat /etc/oratab 
#


# This file is used by ORACLE utilities.  It is created by root.sh
# and updated by either Database Configuration Assistant while creating
# a database or ASM Configuration Assistant while creating ASM instance.

# 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 field 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.
#
#
cndba:/u01/app/oracle/product/12.2.0/db_1:N

再次执行可以看到source database 如下图：