EM 12c: Cluster Database Home Page in Fails to Display Real-time Data with the Message "IO Error: The Network Adapter could not establish the connection"

(Doc ID 2108414.1)

Last updated on AUGUST 29, 2017

Applies to:

Enterprise Manager for Oracle Database - Version 12.1.0.1.0 to 12.1.0.8.0 [Release 12.1]
Information in this document applies to any platform.

Symptoms

In the 12c Enterprise Manager Cloud Control UI, the RAC database target is shown as UP.
But there is a message as below:

Regions that display real-time data will not be displayed. Exception while loading RAC Database Home Page: IO Error: The Network Adapter could not establish
the connection The Connect Descriptor was (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = scan_name)(PORT = 1523))(CONNECT_DATA = (SERVICE_NAME = RAC_ORCL)))

- The <gc_inst>/em/EMGC_OMS1/emoms.trc from the OMS machine shows:

2016-02-03 21:23:11,975 [[ACTIVE] ExecuteThread: '42' for queue: 'weblogic.kernel.Default (self-tuning)'] WARN em.MetricEngine logp.251 - 
Metric rac_orcl::rac_database::HOME_RESOURCES_METRIC contains no cached data!
2016-02-03 21:23:28,414 [RJob Step 73061882] ERROR intg.AlertThresholdTargetUpdateNew logp.251 - AlertThresholdTargetUpdate: Exception occurred:
java.sql.SQLException: IO Error: The Network Adapter could not establish the connection
The Connect Descriptor was (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = scan_name)(PORT = 1523))(CONNECT_DATA = (SERVICE_NAME = RAC_ORCL)))
at oracle.sysman.emSDK.core.util.jdbc.ConnectionFactory.createConnection(ConnectionFactory.java:736)
at oracle.sysman.emInternalSDK.db.conn.DbTargetConnectionFactory.createConnection(DbTargetConnectionFactory.java:517)
.............
2016-02-03 21:28:12,230 [MetricCollector:RACHOMETAB_THREAD550:55] ERROR rt.DbMetricCollectorTarget logp.251 - Exception in getConnection()
rac_orcl:rac_databasejava.sql.SQLException: 
IO Error: The Network Adapter could not establish the connection
The Connect Descriptor was (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = scan_name)(PORT = 1523))(CONNECT_DATA = (SERVICE_NAME = RAC_ORCL)))

-  From the sqlplus on the OMS home, attempting to connect to the target database using the above connection string also fails:

export ORACLE_HOME=<path of the 12c OMS installation>
cd <OMS_HOME>/bin
./sqlplus dbsnmp@"(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=scan_name)(PORT=1523))(CONNECT_DATA=(SERVICE_NAME=RAC_ORCL)))"
SQL*Plus: Release 11.1.0.7.0 - Production on Mon Feb 1 21:10:03 2016
Copyright (c) 1982, 2008, Oracle. All rights reserved.
Enter password:
ERROR:
ORA-12170: TNS:Connect timeout occurred

-  There is a firewall between the OMS machine and the target database server.
-  In this case, the database connectivity from the OMS machine worked if the hostname is used instead of the SCAN listener name.

Cause

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