数据库无法登陆报ORA-21561: OID generation failed错误

[oracle@essc ~]$ sqlplus XIFENFEI/"www.xifenfei.com"@172.16.50.200/orcl

SQL*Plus: Release 11.2.0.4.0 Production on Mon Jun 1 16:52:29 2015

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

ERROR:
ORA-21561: OID generation failed


Enter user-name: 
ERROR:
ORA-12545: Connect failed because target host or object does not exist


Enter user-name: 
ERROR:
ORA-12545: Connect failed because target host or object does not exist


SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus

主机名无法ping通

[root@essc ~]# ping essc
ping: unknown host essc
[root@essc ~]# hostname
essc

[root@essc ~]# more /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.10.11 app1

[oracle@essc ~]$ ifconfig
eth3      Link encap:Ethernet  HWaddr 00:50:56:BB:00:6B  
          inet addr:172.16.10.30  Bcast:172.16.10.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:febb:6b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:9597 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4018 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1549999 (1.4 MiB)  TX bytes:470158 (459.1 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:164 errors:0 dropped:0 overruns:0 frame:0
          TX packets:164 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:11424 (11.1 KiB)  TX bytes:11424 (11.1 KiB)

修改hosts文件
让hosts中含主机名,也就是为了主机名能够ping通

[oracle@essc ~]$ more /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.10.11 app1
172.16.10.30 essc

数据库登录测试

[oracle@essc ~]$ sqlplus XIFENFEI/"www.xifenfei.com"@172.16.50.200/orcl

SQL*Plus: Release 11.2.0.4.0 Production on Mon Jun 1 16:56:39 2015

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> 
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

具体见官方说明
Ora-21561: OID Generation Failed (Doc ID 1335327.1)

APPLIES TO:
Oracle Net Services - Version 9.2.0.8 to 11.2.0.3 [Release 9.2 to 11.2]
Information in this document applies to any platform.
***Checked for relevance on 14-Jan-2013*** 

SYMPTOMS
When attempting to connect to the database using SQL*Plus or DBCA, 
the following error occurs intermittently:

ERROR
-----------------------
ORA-21561: OID generation failed

CAUSE
This could be caused by not having the host name for the 
target database fully qualified in the hosts file.
To verify if you are hitting this issue, the following symptoms should be met:

- ORA-21561: OID generation failed.
- Hosts file has un-fully qualified entry for the target database host:

127.0.0.1 loopback localhost # loopback (lo0) name/address 
10.210.9.111 dbhost
In this sample, dbhost is the target db host.

This is reported in an unpublished Bug 12597261: 
"ORA-21561 IF HOSTNAME ENVIRONMENT VARIABLE IS NOT FULLY QUALIFIED",
 which should be resolved as of 12G.

SOLUTION
Modify the hosts file to have the fully qualified host names, 
by adding the fully qualified domain name to the entry.

127.0.0.1 loopback localhost # loopback (lo0) name/address 
10.210.9.111 dbhost.sample.com

Verify that other environment and service handles are properly defined as well.

If this is a Windows environment, please check : 
Windows: Connections Fail with ORA-12640 or ORA-21561 (Doc ID 744125.1)

再次建议:修改主机名请修改完全,具体参考：linux上安装oracle10g注意事项中修改主机名部分