Connecting to the Oracle Database

Connection String Attributes

Table 3-1 lists the supported connection string attributes.

The following example uses connection string attributes to connect to an Oracle Database:

// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class ConnectionSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    //using connection string attributes to connect to Oracle Database
    con.ConnectionString = "User Id=scott;Password=tiger;Data Source=oracle";
    con.Open();
    Console.WriteLine("Connected to Oracle" + con.ServerVersion);
    
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
    Console.WriteLine("Disconnected");
  }
}

Connection Pooling

ODP.NET connection pooling is enabled and disabled using the Pooling connection string attribute. By default, connection pooling is enabled. The following are ConnectionString attributes that control the behavior of the connection pooling service:

• Pooling

• Connection Lifetime

• Connection Timeout

• Max Pool Size

• Min Pool Size

• Incr Pool Size

• Decr Pool Size

• Validate Connection

Connection Pooling Example

The following code opens a connection using ConnectionString attributes related to connection pooling.

// C#
 
using System;
using Oracle.DataAccess.Client; 
 
 
class ConnectionPoolingSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    //Open a connection using ConnectionString attributes
    //related to connection pooling.
    con.ConnectionString = 
      "User Id=scott;Password=tiger;Data Source=oracle;" + 
      "Min Pool Size=10;Connection Lifetime=120;Connection Timeout=60;" + 
      "Incr Pool Size=5; Decr Pool Size=2";
    con.Open();
    Console.WriteLine("Connection pool successfully created");
 
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
    Console.WriteLine("Connection is placed back into the pool.");
  }
}

Operating System Authentication

The Oracle Database can use Windows user login credentials to authenticate database users. To open a connection using Windows user login credentials, the User Id ConnectionString attribute must be set to /. If Password is provided, it is ignored.

/* Create an OS-authenticated user in the database
   Assume init.ora does not have OS_AUTHENT_PREFIX set &
   a local OS user called 'FooUser' exists with the password 'FooUser':
 
     create user OPS$FooUser identified by FooUser;
     grant connect, resource to OPS$FooUser;
 
   Login as FooUsers and execute the sample
   See documentation for details on how to configure an OS-Authenticated user
*/
 
// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class OSAuthenticationSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    //Establish connection using OS Authentication   
    con.ConnectionString = "User Id=/;Data Source=oracle;";
    con.Open();
    Console.WriteLine("Connected to Oracle" + con.ServerVersion);
 
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
    Console.WriteLine("Disconnected");
  }
}

Privileged Connections

Oracle allows database administrators to connect to an Oracle Database with either SYSDBA or SYSOPER privileges. This is done through the DBA Privilege attribute of the ConnectionString.

The following example connects SYS/SYS as SYSDBA:

// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class PrivilegedConnectionSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    //Connect SYS/SYS as SYSDBA   
    con.ConnectionString = "User Id=SYS;Password=SYS;" + 
      "DBA Privilege=SYSDBA;Data Source=oracle;";
    con.Open();
    Console.WriteLine("Connected to Oracle" + con.ServerVersion);
 
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
    Console.WriteLine("Disconnected");
  }
}

Password Expiration

Oracle allows users' password to expire. ODP.NET lets applications handle the password expiration by providing a new method, OpenWithNewPassword, that opens the connection with a new password.

The following code snippet uses the OracleConnection OpenWithNewPassword method to connect with a new password of panther:

/* Database Setup
connect / as sysdba;
drop user testexpire cascade;
-- create user "testexpire" with password "testexpire"
grant connect , resource to testexpire identified by testexpire; 
alter user testexpire password expire;
*/
 
 
// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class PasswordExpirationSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    try
    {
      con.ConnectionString = 
        "User Id=testexpire;Password=testexpire;Data Source=oracle";
      con.Open();
      Console.WriteLine("Connected to Oracle" + con.ServerVersion);
    }
    catch (OracleException ex)
    {
      Console.WriteLine(ex.Message);
 
      //check the error number 
      //ORA-28001 : the password has expired
      if (ex.Number == 28001)
      {
        Console.WriteLine("\nChanging password to panther");
        con.OpenWithNewPassword("panther");
        Console.WriteLine("Connected with new password.");
      }
    }
    finally
    {
      // Close and Dispose OracleConnection object
      con.Close();
      con.Dispose();
      Console.WriteLine("Disconnected");
    }
  }
}

Proxy Authentication

The Oracle Database allows a middle-tier server to connect to proxy clients in a secure fashion.

In multitier environments, proxy authentication allows control of middle-tier application security by preserving client identities and privileges through all tiers, and by auditing actions taken on behalf of clients. The proxy authentication feature allows the identity of a user (user id and password) using a Web application to be passed through the application to the database server.

ODP.NET supports proxy authentication with or without a client password by providing the Proxy User Id and Proxy Password attributes of the ConnectionString property.

/* Create a proxy user and modified scott to allow proxy connection:
     create user appserver identified by eagle;
     grant connect, resource to appserver;
     alter user scott grant connect through appserver;
*/
 
// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class ProxyAuthenticationSample
{
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    // Connecting using proxy authentication
    con.ConnectionString = "User Id=scott;Password=tiger;" + 
      "Data Source=oracle;Proxy User Id=appserver;Proxy Password=eagle; ";
    con.Open();
    Console.WriteLine("Connected to Oracle" + con.ServerVersion);
 
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
    Console.WriteLine("Disconnected");
  }
}

Transparent Application Failover (TAF) Callback Support

Transparent Application Failover (TAF) is a feature in the Oracle Database that provides high availability.

TAF enables an application connection to automatically reconnect to a database if the connection fails. Active transactions roll back, but the new database connection, made by way of a different node, is identical to the original. This is true regardless of how the connection fails.

With Transparent Application Failover, a client notices no loss of connection as long as there is one instance left serving the application. The database administrator controls which applications run on which instances and also creates a failover order for each application.

// C#
 
using System;
using Oracle.DataAccess.Client; 
 
class TAFCallBackSample
{
  public static FailoverReturnCode OnFailover(object sender, 
                                              OracleFailoverEventArgs eventArgs)
  {
    switch (eventArgs.FailoverEvent)
    {
      case FailoverEvent.Begin :
        Console.WriteLine(
          " \nFailover Begin - Failing Over ... Please standby \n");
        Console.WriteLine(
          " Failover type was found to be " + eventArgs.FailoverType);
        break;
 
      case FailoverEvent.Abort :
        Console.WriteLine(" Failover aborted. Failover will not take place.\n");
        break;
 
      case FailoverEvent.End :
        Console.WriteLine(" Failover ended ...resuming services\n");
        break;
 
      case FailoverEvent.Reauth :
        Console.WriteLine(" Failed over user. Resuming services\n");
        break;
 
      case FailoverEvent.Error :
        Console.WriteLine(" Failover error gotten. Sleeping...\n");
        return FailoverReturnCode.Retry;
 
      default :
        Console.WriteLine("Bad Failover Event: %d.\n", eventArgs.FailoverEvent);
        break;
    }
    return FailoverReturnCode.Success;
  } /* OnFailover */
 
  static void Main()
  {
    OracleConnection con = new OracleConnection();
 
    con.ConnectionString = "User Id=scott;Password=tiger;Data Source=oracle;";
    con.Open();
    con.Failover += new OracleFailoverEventHandler(OnFailover);
    Console.WriteLine("Event Handler is successfully registered");
 
    // Close and Dispose OracleConnection object
    con.Close();
    con.Dispose();
  }
}