Oracle案例04——TNS-12547: TNS:lost contact

Oracle数据库服务器DG从库重启后，无法完成数据同步，具体报错信息如下：

一、报错信息

alter log报错

***********************************************************************

Fatal NI connect error 12547, connecting to:

  VERSION INFORMATION:
        TNS for Linux: Version 11.2.0.3.0 - Production
        TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.3.0 - Production
  Time: 23-APR-2018 10:30:45
  Tracing not turned on.
  Tns error struct:
    ns main err code: 12547

TNS-12547: TNS:lost contact
    ns secondary err code: 12560
    nt main err code: 517

TNS-00517: Lost contact
    nt secondary err code: 104
    nt OS err code: 0
Error 12547 received logging on to the standby
FAL[client, USER]: Error 12547 connecting to LOGDB for fetching gap sequence

二、错误原因分析

根据报错信息可以看到通过tns连接logdb服务名存在问题，可通过排查监听是否启动，是否有防火墙限制等。

三、处理步骤

通过排查监听和防火墙限制，发现没有问题，主库通过tns服务名连接正常，从库通过tnsping报错

[oracle@dg ~]$ tnsping logdb

TNS Ping Utility for Linux: Version 11.2.0.3.0 - Production on 23-APR-2018 11:26:28

Copyright (c) 1997, 2011, Oracle.  All rights reserved.

Used parameter files:


Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 1xx.xx.xx.xx)(PORT = 1521))) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = logdb)))
TNS-12547: TNS:lost contact

从库通过telnet 主库IPaddr 1521端口检查，发现连接上后直接被关闭

# telnet  1xx.xx.xx.xx 1521   
Trying 1xx.xx.xx.xx...
Connected to 1xx.xx.xx.xx.
Escape character is '^]'.
Connection closed by foreign host.

这里基本可以断定是监听问题，具体检查后发现只sqlnet.ora做了监听限制

tcp.validnode_checking=yes
tcp.invited_nodes=(ip1,ip2,ip3,ip4,ip5,ip6)

将备库IP添加进允许访问列表即可，然后通过tnsping检查连接正常，然后通过手动恢复主备同步。

（DG主备同步恢复过程略）