title: ORACLE : Io exception: The Network Adapter could not establish the connection
body: <p>We are getting this error sporadically. With the same TNS, we are able to make proper connections to the database. But we see this in the logs while make connections some times. Following is the stack trace. This is db connection to Oracle from a Linux machine and java application Any help is appreciated.</p>
  
  <blockquote>
    <p>java.sql.SQLException: Io exception: The Network Adapter could not establish the connection
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:255)
        at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:387)
        at oracle.jdbc.driver.PhysicalConnection.(PhysicalConnection.java:439)
        at oracle.jdbc.driver.T4CConnection.(T4CConnection.java:165)
        at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:35)
        at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:801)
        at oracle.jdbc.pool.OracleDataSource.getPhysicalConnection(OracleDataSource.java:297)
        at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:221)
        at oracle.jdbc.pool.OracleConnectionPoolDataSource.getPhysicalConnection(OracleConnectionPoolDataSource.java:157)
        at oracle.jdbc.pool.OracleConnectionPoolDataSource.getPooledConnection(OracleConnectionPoolDataSource.java:94)
        at oracle.jdbc.pool.OracleImplicitConnectionCache.makeCacheConnection(OracleImplicitConnectionCache.java:1567)
        at oracle.jdbc.pool.OracleImplicitConnectionCache.getCacheConnection(OracleImplicitConnectionCache.java:478)
        at oracle.jdbc.pool.OracleImplicitConnectionCache.getConnection(OracleImplicitConnectionCache.java:347)
        at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:404)
        at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:189)
        at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:165)</p>
  </blockquote>