4 Introduction to Automatic Workload Management

Using Oracle Services

To manage workloads or a group of applications, you can define services that you assign to a particular application or to a subset of an application's operations. You can also group work by type under services. For example, online users can be a service while batch processing can be another and reporting can be yet another service type.

Oracle recommends that all users who share a service have the same service level requirements. You can define specific characteristics for services and each service can be a separate unit of work. There are many options that you can take advantage of when using services. Although you do not have to implement these options, using them helps optimize application performance.

When you define a service, you define which instances normally support that service. These are known as the PREFERRED instances. You can also define other instances to support a service if the service's preferred instance fails. These are known as AVAILABLE instances.

When you specify PREFERRED instances, you are specifying the number of instances on which a service will normally run. Oracle Clusterware attempts to ensure that the service always runs on the number of instances for which you have configured the service. Afterwards, due to either instance failure or planned service relocations, a service may be running on an AVAILABLE instance. You cannot control which AVAILABLE instance to which Oracle Clusterware relocates the services if there is more than one in the list. When a service moves to an AVAILABLE instance, Oracle does not move the service back to the PREFERRED instance when the PREFERRED instance restarts because:

• The service is already running on the desired number of instances

• Maintaining the service on the current instance provides a higher level of service availability

• Not moving the service back to the initial PREFERRED instance prevents a second outage

You can, however, easily automate fail back by using FAN callouts.

Resource profiles are automatically created when you define a service. A resource profile describes how Oracle Clusterware should manage the service and which instance the service should failover to if the preferred instance stops. Resource profiles also define service dependencies for the instance and the database. Due to these dependencies, if you stop a database, then the instances and services are automatically stopped in the correct order.

Services are integrated with Resource Manager, which enables you to restrict the resources that are used by the users who connect with a service in an instance. The Resource Manager enables you to map a consumer group to a service so that users who connect with the service are members of the specified consumer group. Also, the Automatic Workload Repository (AWR) enables you to monitor performance by service.

Oracle Net Services provides connection load balancing to enable you to spread user connections across all of the instances that are supporting a service. For each service, you can define the method that you want the listener to use for load balancing by setting the connection load balancing goal, CLB_GOAL. You can also specify a single transparent application failover (TAF) policy for all users of a service by defining the FAILOVER_METHOD, FAILOVER_TYPE, and so on. (See the Oracle Database Net Services Administrator's Guide for more information about configuring TAF.)

Oracle RAC uses FAN to notify applications about configuration changes and the current service level that is provided by each instance where the service is enabled. FAN has two methods for publishing events to clients, the Oracle Notification Service (ONS) that is used by Java Database Connectivity (JDBC) clients including the Oracle Application Server, and Oracle Streams, and Advanced Queueing that is used by Oracle Call Interface (OCI) and Oracle Data Provider for .NET (ODP.NET) clients. When using Advanced Queueing, you must enable the service to use the queue by setting AQ_HA_NOTIFICATIONS to true.

With runtime connection load balancing, applications can use load balancing advisory events to provide better service to users. The Oracle JDBC and ODP.NET clients are automatically integrated to take advantage of load balancing advisory events. The load balancing advisory informs the client about the current service level that an instance is providing for a service. The load balancing advisory also recommends how much of the workload should be sent to that instance. In addition, Oracle Net Services provides connection load balancing to enable you to spread user connections across all of the instances that support a service. To enable the load balancing advisory, set the GOAL parameter on the service.

Distributed transaction processing applications have unique requirements. To make it easier to use Oracle RAC with global transactions, set the distributed transaction processing parameter on the service so that all tightly coupled branches of a distributed transaction processing transaction are run on the same instance.

Default Service Connections

A special Oracle database service is created by default for your Oracle RAC database. This default service is always available on all instances in an Oracle RAC environment, unless an instance is in restricted mode. You cannot alter this service or its properties. The database also supports the following two internal services:

• SYS$BACKGROUND is used by the background processes only

• SYS$USERS is the default service for user sessions that are not associated with any application service

Both of these internal services support all of the automatic workload management features. You cannot stop or disable either of these internal services.

Connection Load Balancing

Oracle Net Services provides the ability to balance client connections across the instances in an Oracle RAC configuration. There are two types of load balancing that you can implement: client-side and server-side load balancing. Client-side load balancing balances the connection requests across the listeners. With server-side load balancing, the listener directs a connection request to the best instance currently providing the service by using the load balancing advisory. In an Oracle RAC database, client connections should use both types of connection load balancing.

FAN, Fast Connection Failover, and the load balancing advisory depend on an accurate connection load balancing configuration that includes setting the connection load balancing goal for the service. You can use a goal of either LONG or SHORT for connection load balancing. These goals have the following characteristics:

• LONG—Use the LONG connection load balancing method for applications that have long-lived connections. This is typical for connection pools and SQL*Forms sessions. LONG is the default connection load balancing goal. The following is an example of modifying a service, POSTMAN, with the PL/SQL DBMS_SERVICE package and the CLB_GOAL_LONG package constant to define the connection load balancing goal for long-lived sessions:

  EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'POSTMAN' 
          , clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);
  

• SHORT—Use the SHORT connection load balancing method for applications that have short-lived connections. The following example modifies the service known as ORDER, using the DBMS_SERVICE.CLB_GOAL_SHORT package constant to set the goal to SHORT:

  EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'ORDER' 
          , CLB_GOAL => DBMS_SERVICE.CLB_GOAL_SHORT);
  

When you create an Oracle RAC database with the DBCA, it automatically:

• Configures and enables server-side load balancing

• Sets the local and remote listener parameters (Note: If you do not use DBCA, you should set the LOCAL_LISTENER and REMOTE_LISTENER database parameters manually, especially if you do not use port 1521.)

• Creates a sample client-side load balancing connection definition in the tnsnames.ora file on the server

When Oracle Net Services establishes a connection to an instance, the connection remains open until the client closes the connection, the instance is shutdown, or a failure occurs. If you configure TAF for the connection, then Oracle Database moves the session to a surviving instance when an outage occurs.

TAF can restart a query after failover has completed but for other types of transactions, such as INSERT, UPDATE, or DELETE, the application must rollback the failed transaction and resubmit the transaction. You must reexecute any session customizations, in other words, ALTER SESSION statements, after failover has occurred. However, with TAF, a connection is not moved during normal processing, even if the workload changes over time.

Services simplify the deployment of TAF. You can define a TAF policy for a service and all connections using this service will automatically have TAF enabled. This does not require any client-side changes. The TAF setting on a service overrides any TAF setting in the client connection definition. To define a TAF policy for a service, use the DBMS_SERVICE PL/SQL procedure as in the following example:

EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'gl.us.oracle.com' 
, aq_ha_notifications => TRUE 
, failover_method => DBMS_SERVICE.FAILOVER_METHOD_BASIC 
, failover_type => DBMS_SERVICE.FAILOVER_TYPE_SELECT 
, failover_retries => 180 
, failover_delay => 5 
, clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);

Client-side load balancing is defined in your client connection definition by setting the parameter LOAD_BALANCE=ON (the default is ON for description lists). When you set this parameter to ON, Oracle randomly selects an address in the address list, and connects to that node's listener. This balances client connections across the available listeners in the cluster. When the listener receives the connection request, the listener connects the user to an instance that the listener knows provides the requested service. To see what services a listener supports, run the lsnrctl services command.

In addition to client-side load balancing, Oracle Net Services include connection failover. If an error is returned from the chosen address in the list, Oracle Net Services will try the next address in the list until it is either successful or it has exhausted all addresses in its list. To increase availability, you can specify a timeout within which Oracle Net will wait for a response from the listener.

You can avoid delays by setting the oracle.net.ns.SQLnetDef.TCP_CONNTIMEOUT_STR property, as follows:

Properties prop = new Properties ();
prop.put (oracle.net.ns.SQLnetDef.TCP_CONNTIMEOUT_STR,
"" + (1 * 1000)); // 1 second
dbPools[ poolIndex ].setConnectionProperties ( prop );

The parameter value is specified in milliseconds. Therefore, it is possible to reduce the timeout to 500Ms if the application retries connecting.

For OCI clients, create a local sqlnet.ora file on the client side. Configure the connection timeout in this file by adding the following line:

sqlnet.outbound_connect_timeout = 1

The granularity of the timeout value for the OCI client is in seconds.

Overview of Fast Application Notification

FAN is a notification mechanism that Oracle RAC uses to notify other processes about configuration and service level information that includes service status changes, such as UP or DOWN events. Applications can respond to FAN events and take immediate action. FAN UP and DOWN events can apply to instances, services, and nodes.

For cluster configuration changes, the Oracle RAC high availability framework publishes a FAN event immediately when a state change occurs in the cluster. Instead of waiting for the application to poll the database and detect a problem, applications can receive FAN events and react immediately.

FAN also publishes load balancing advisory events. Applications can take advantage of the load balancing advisory FAN events to direct work requests to the instance in the cluster that is currently providing the best service quality. You can take advantage of FAN events in the following three ways:

1. Your application can use FAN without programmatic changes if you use an integrated Oracle client. The integrated clients for FAN events include Oracle Database JDBC, Oracle Database ODP.NET, and Oracle Database OCI. This includes applications that use TAF. The integrated Oracle clients must be Oracle Database 10g Release 2 or later to take advantage of the load balancing advisory FAN events. (See the Oracle Database Net Services Administrator's Guide for more information about configuring TAF.)

2. Applications can use FAN programmatically by using the ONS Application Programming Interface (API) to subscribe to FAN events and to execute event handling actions upon the receipt of an event.

3. You can implement FAN with server-side callouts on your database tier.

For DOWN events, the disruption to the application can be minimized because sessions to the failed instance or node can be terminated. Incomplete transactions can be terminated and the application user is immediately notified. Application users who request connections are directed to available instances only. For UP events, when services and instances are started, new connections can be created so that the application can immediately take advantage of the extra resources. Through server-side callouts, you can also use FAN to:

• Log status information

• Page DBAs or to open support tickets when resources fail to start

• Automatically start dependent external applications that need to be co-located with a service

• Change resource plans or to shut down services when the number of available instances decreases, for example, if nodes fail

• Automate the fail back of a service to PREFERRED instances if needed

FAN events are published using ONS and an Oracle Streams Advanced Queuing. The publication mechanisms are automatically configured as part of your Oracle RAC installation.

The Connection Manager (CMAN) and Oracle Net Services listeners are integrated with FAN events. This enables the listener and CMAN to immediately de-register services provided by the failed instance and to avoid erroneously sending connection requests to failed instances.

If you use the service goal CLB_GOAL_SHORT, then the listener uses the load balancing advisory when the listener balances the connection loads. When load balancing advisory is enabled, the metrics used for the listener are finer grained.

Application High Availability with Services and FAN

Oracle Database focuses on maintaining service availability. In Oracle RAC, Oracle services are designed to be continuously available with loads shared across one or more instances. The Oracle RAC high availability framework maintains service availability by using Oracle Clusterware and resource profiles.

The Oracle RAC high availability framework monitors the database and its services and sends event notifications using FAN. Oracle Clusterware recovers and balances services according to business rules.

Managing Unplanned Outages

You can assign services in Oracle RAC to one or more instances. If Oracle RAC detects an outage, then Oracle Clusterware isolates the failed component and recovers the dependent components. For services, if the failed component is an instance, then Oracle Clusterware relocates the service to an available instance in the cluster. FAN events can occur at various levels within the Oracle Database architecture and are published through ONS and Advanced Queuing. You can also program notification using FAN callouts.

Notification occurs from a surviving node when the failed node is out of service. The location and number of instances in an Oracle RAC environment that provide a service are transparent to applications. Restart and recovery are automatic, including the restarting of the subsystems, such as the listener and the Automatic Storage Management (ASM) processes, not just the database. You can use FAN callouts to report faults to your fault management system and to initiate repair jobs.

Managing Planned Outages

For repairs, upgrades, and changes that require you to isolate one or more instances, Oracle RAC provides interfaces that relocate, disable, and enable services to minimize service disruption to application users. Once you complete the operation, you can return the service to normal operation.

Due to dependencies, if you manually shutdown your database, then all of your services automatically stop. If you then manually restart the database, then you must also restart the database's services. Use FAN callouts to automate starting the services when the database starts.

Fast Application Notification High Availability Events

Table 4-1 describes the FAN event record parameters and the event types, followed by name-value pairs for the event properties. The event type is always the first entry and the timestamp is always the last entry as in the following example:

FAN event type: service_member
Properties: version=1.0 service=ERP database=FINPROD instance=FINPROD3 host=node3 status=up

A FAN record matches the database signature of each session as shown in Table 4-2.

Using Fast Application Notification Callouts

FAN callouts are server-side executables that Oracle RAC executes immediately when high availability events occur. You can use FAN callouts to automate the following activities when events occur in a cluster configuration, such as:

• Opening fault tracking tickets

• Sending messages to pagers

• Sending e-mail

• Starting and stopping server-side applications

• Maintaining an uptime log by logging each event as it occurs

• Relocating low-priority services when high priority services come online

To use FAN callouts, place an executable in the directory CRS_home/racg/usrco on every node that runs Oracle Clusterware. If you are using scripts, then set the shell as the first line of the executable. The following is an example file for the CRS_home/racg/usrco/callout.sh callout:

#! /bin/ksh
FAN_LOGFILE= [your path name]/admin/log/`hostname`_uptime.log
echo $* "reported="`date` >> $FAN_LOGFILE &

The following output is from the previous example:

NODE VERSION=1.0 host=sun880-2 incarn=23 status=nodedown reason=
timestamp=08-Oct-2004 04:02:14 reported=Fri Oct 8 04:02:14 PDT 2004

Example callout scripts are available in the Oracle Real Application Clusters Sample Code section on Oracle Technology Network at http://www.oracle.com/technology/sample_code/products/rac/

A FAN record matches the database signature of each session, as shown in Table 4-2, "FAN Parameters and Matching Database Signatures". The signature information is also available using OCI_ATTRIBUTES. These attributes are available in the OCI Connection Handle. Use this information to take actions on sessions that match the FAN event data.

Overview of the Load Balancing Advisory

Load balancing distributes work across all of the available Oracle RAC database instances. Oracle recommends that applications use persistent connections that span the instances that offer a particular service. Connections are created infrequently and exist for a long duration. Work comes into the system with high frequency, borrows these connections, and exists for a relatively short duration. The load balancing advisory provides advice about how to direct incoming work to the instances that provide the optimal quality of service for that work. This minimizes the need to relocate the work later.

By using the THROUGHPUT or SERVICE_TIME goals, feedback is built in to the system. Work is routed to provide the best service times globally, and routing responds gracefully to changing system conditions. In a steady state, the system approaches equilibrium with improved throughput across all of the Oracle RAC instances.

Standard architectures that can use the load balancing advisory include connection load balancing, transaction processing monitors, application servers, connection concentrators, hardware and software load balancers, job schedulers, batch schedulers, and message queuing systems. All of these applications can allocate work.

The load balancing advisory is deployed with key Oracle clients, such as a listener, the JDBC Implicit Connection Cache, and the ODP.NET Connection Pool. The load balancing advisory is also open for third-party subscription by way of ONS.

Configuring Your Environment to Use the Load Balancing Advisory

You can configure your environment to use the load balancing advisory by defining service-level goals for each service for which you want to enable load balancing. This enables the load balancing advisory for that service and FAN load balancing events are published. There are two types of service-level goals for runtime:

• SERVICE TIME—Attempts to direct work requests to instances according to response time. Load balancing advisory data is based on elapsed time for work done in the service plus available bandwidth to the service. An example for the use of SERVICE TIME is for workloads such as internet shopping where the rate of demand changes:

  EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'OE' -
  , goal => DBMS_SERVICE.GOAL_SERVICE_TIME -
  , clb_goal => DBMS_SERVICE.CLB_GOAL_SHORT);
  

• THROUGHPUT—Attempts to direct work requests according to throughput. The load balancing advisory is based on the rate that work is completed in the service plus available bandwidth to the service. An example for the use of THROUGHPUT is for workloads such as batch processes, where the next job starts when the last job completes:

  EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'sjob' -
          , goal => DBMS_SERVICE.GOAL_THROUGHPUT -
         , clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);
  

  Setting the goal to NONE disables load balancing for the service. You can see the goal settings for a service in the data dictionary and in the DBA_SERVICES, V$SERVICES, and V$ACTIVE_SERVICES views.

  See Also:

  "Administering Services" for more information about administering services and adding goals to services

Load Balancing Advisory FAN Events

The load balancing advisory FAN events provide metrics for load balancing algorithms. The easiest way to take advantage of these events is to use the runtime connection load balancing feature of an Oracle integrated client such as JDBC, ODP.NET, or OCI. Client applications can subscribe to these events directly by way of the ONS API. Table 4-3 describes the load balancing advisory FAN event parameters.

Use the following example to monitor load balancing advisory events:

SET PAGES 60 COLSEP '|' LINES 132 NUM 8 VERIFY OFF FEEDBACK OFF
COLUMN user_data HEADING "AQ Service Metrics" FORMAT A60 WRAP
BREAK ON service_name SKIP 1
SELECT
 TO_CHAR(enq_time, 'HH:MI:SS') Enq_time, user_data
 FROM sys.sys$service_metrics_tab
 ORDER BY 1 ;

Enabling JDBC Clients for Fast Connection Failover

Enabling FAN for the Oracle JDBC Implicit Connection Cache enables FAN high availability events and the load balancing advisory. Your application can use the JDBC development environment for either thick or thin JDBC clients to use FAN. You must use the JDBC Implicit Connection Cache to enable the FAN features of Fast Connection Failover and runtime connection load balancing.

To configure the JDBC client, set the FastConnectionFailoverEnabled property before making the first getConnection() request to a data source. When you enable Fast Connection Failover, the failover applies to every connection in the connection cache. If your application explicitly creates a connection cache using the Connection Cache Manager, then you must first set FastConnectionFailoverEnabled.

Enabling Oracle Call Interface Clients for Fast Connection Failover

OCI clients can enable Fast Connection Failover by registering to receive notifications about Oracle RAC high availability FAN events and respond when events occur. This improves the session failover response time in OCI and also removes terminated connections from connection and session pools. This feature works on OCI applications, including those that use TAF, connection pools, or session pools.

First, you must enable a service for high availability events. This automatically populates the advanced queuing ALERT_QUEUE. If your application is using TAF, then enable the TAF settings for the service. Configure client applications to connect to an Oracle RAC database. Clients can register callbacks that are used whenever an event occurs. This reduces the time that it takes to detect a connection failure. During DOWN event processing, OCI:

• Terminates affected connections at the client and returns an error

• Removes connections from the OCI connection pool and the OCI session pool—the session pool maps each session to a physical connection in the connection pool, and there can be multiple sessions for each connection

• Fails over the connection if you have configured TAF

If TAF is not configured, then the client only receives an error.

Perform the following steps to configure Fast Connection Failover with an OCI client:

1. Ensure that the service that you are using has Advanced Queuing notifications enabled by setting the services' values of AQ_HA_NOTIFICATIONS to TRUE. For example:

   EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'gl.us.oracle.com' 
           , aq_ha_notifications => TRUE 
           , failover_method  => DBMS_SERVICE.FAILOVER_METHOD_BASIC 
           , failover_type    => DBMS_SERVICE.FAILOVER_TYPE_SELECT 
           , failover_retries => 180 
           , failover_delay   => 5 
           , clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);
   

2. Enable OCI_EVENTS at environment creation time on the client as follows:

   ( OCIEnvCreate(...) )
   

3. Client applications must link with the client thread or operating system library.

4. Optionally register a client EVENT callback

To see the alert information, you can query the views DBA_OUTSTANDING_ALERTS and DBA_ALERT_HISTORY.

Enabling Oracle Call Interface Clients for Runtime Connection Load Balancing

As of Oracle Database 11g Release 1 (11.1), Oracle Call Interface (OCI) session pooling enables multiple threads of an application to use a dynamically managed set of pre-created database sessions. Oracle continually reuses the sessions in the pool to form nearly permanent channels to the instances, thus saving the overhead of creating and closing sessions every time applications need them.

To fully optimize session pools with Oracle RAC, sessions given to the requesting threads are appropriately mapped to instances based on the instance load. The OCI session pools use service metrics information received from the Load Balancing Advisory in Oracle RAC to allocate the sessions, resulting in better performance

OCI dynamically maps sessions to the threads based on the instance load. It uses service metrics provided by the Load Balancing Advisory to perform runtime connection load balancing.^Foot 1  The number of connections can exceed the number of threads at certain times, but the OCI eventually adjusts this automatically, without any need for user intervention.

If the session pool supports services that span multiple instances, then the work requests are distributed across instances so that the instances providing better service are given more requests. For session pools that support services at only one instance, the first available session in the pool is adequate.

Runtime connection load balancing is enabled by default in a Oracle Database Release 11.1 (or higher) client talking to a server running Oracle Database Release 10.2 (or higher). To disable runtime connection load balancing, set the mode parameter to OCI_SPC_NO_RLB when calling OCISessionPoolCreate().

To receive the service metrics based on the service time, ensure you have met the following conditions:

1. Link the application with the threads library.

2. Create the OCI environment in OCI_EVENTS and OCI_THREADED mode.

3. Enable event notification for the service for which the session pool is created.

   To enable event notification, use the DBMS_SERVICE.MODIFY_SERVICE procedure and set the Advanced Queuing AQ_HA_NOTIFICATIONS parameter to TRUE.

4. Modify the service to set up its service goal and clb_goal, as shown in the following example for the myService service:

   EXEC DBMS_SERVICE.MODIFY_SERVICE(''myService'', 
   DBMS_SERVICE.GOAL_SERVICE_TIME,
   DBMS_SERVICE.CLB_GOAL=SHORT);
   

Enabling ODP.NET Clients to Receive FAN High Availability Events

Oracle Data Provider for .NET (ODP.NET) connection pools can subscribe to notifications that indicate when nodes, services, and service members are down. After a DOWN event, Oracle Database cleans up sessions in the connection pool that go to the instance that stops and ODP.NET proactively disposes connections that are no longer valid. ODP.NET establishes connections to existing Oracle RAC instances if the removal of severed connections brings the total number of connections below the value that is set for the MIN_POOL_SIZE parameter.

The procedures for enabling ODP.NET are similar to the procedures for enabling JDBC in that you must set parameters in the connection string to enable Fast Connection Failover. Perform the following steps to enable FAN:

1. Enable Advanced Queuing notifications by using the DBMS.SERVICE package as in the following example:

2. EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'gl.us.oracle.com' 
           , aq_ha_notifications => TRUE 
           , clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);
   

3. Enable Fast Connection Failover for ODP.NET connection pools by subscribing to FAN high availability events. Do this by setting the ha events connection string attribute to true at connection time. Note that this only works if you are using connection pools. In other words, do this if you have set the pooling attribute to true, which is the default. The following example shows this in more detail:

   // C#
   using System;
   using Oracle.DataAccess.Client;
    
   class HAEventEnablingSample
   {
     static void Main()
     {
       OracleConnection con = new OracleConnection();
    
       // Open a connection using ConnectionString attributes
       // Also, enable "load balancing"
       con.ConnectionString =
         "User Id=scott;Password=tigercat;Data Source=oracle;" +
         "Min Pool Size=10;Connection Lifetime=120;Connection Timeout=60;" +
         "HA Events=true;Incr Pool Size=5;Decr Pool Size=2";
    
       con.Open();
    
       // Create more connections and carry out work against the DB here.
    
       // Dispose OracleConnection object
       con.Dispose();
     }
   }
   

Enabling ODP.NET Clients to Receive FAN Load Balancing Advisory Events

Use the following procedures to enable ODP.NET to receive FAN load balancing advisory events:

1. Enable Advanced Queuing notifications by using the DBMS.SERVICE package, as in the following example:

   EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name => 'gl.us.oracle.com' 
           , aq_ha_notifications => TRUE 
           , failover_method  => DBMS_SERVICE.FAILOVER_METHOD_BASIC 
           , failover_type    => DBMS_SERVICE.FAILOVER_TYPE_SELECT 
           , failover_retries => 180 
           , failover_delay   => 5 
           , clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);
   

2. Set the GOAL and CLB_GOAL for the service and ensure that Oracle Net Services is configured for connection load balancing.

3. To take advantage of load balancing events with ODP.NET connection pools, set the load balancing string to TRUE; the default is FALSE. You can do this at connect time. This only works if you are using connection pools, or when the pooling attribute is set to TRUE which is the default, as in the following example:

   // C#
   using System;
   using Oracle.DataAccess.Client;
    
   class LoadBalancingEnablingSample
   {
     static void Main()
     {
       OracleConnection con = new OracleConnection();
    
       // Open a connection using ConnectionString attributes
       // Also, enable "load balancing"
       con.ConnectionString =
         "User Id=scott;Password=tigercat;Data Source=oracle;" +
         "Min Pool Size=10;Connection Lifetime=120;Connection Timeout=60;" +
         "Load Balancing=true;Incr Pool Size=5;Decr Pool Size=2";
    
       con.Open();
    
       // Create more connections and carry out work against the DB here.
    
       // Dispose OracleConnection object
       con.Dispose();
     }
   }
   

Administering Services with Enterprise Manager

The Cluster Managed Database Services page is the master page for beginning all tasks related to services. To access this page, go to the Cluster Database Availability page, then click Cluster Managed Database Services in the Services section. You can use this page and drill down from this page to:

• View a list of services for the cluster

• View the instances on which each service is currently running

• View the status for each service

• Create or edit a service

• Start or stop a service

• Enable or disable a service

• Perform instance-level tasks for a service

• Delete a service

Administering Services with the PL/SQL DBMS_SERVICE Package

You can manage services with the PL/SQL DBMS_SERVICE package procedures described in Table 4-4.

Administering Services with SRVCTL

When you create a service with SRVCTL, you must start it with a separate SRVCTL command. However, you may later need to manually stop or restart the service. You may also need to disable the service to prevent automatic restarts, to manually relocate the service, or obtain status information about the service. The following sections explain how to use SRVCTL to perform the following administrative tasks:

• Creating Services with SRVCTL

• Starting and Stopping Services with SRVCTL

• Enabling and Disabling Services with SRVCTL

• Relocating Services with SRVCTL

• Obtaining the Statuses of Services with SRVCTL

• Obtaining the Configuration of Services with SRVCTL

srvctl add service -d database_unique_name -s service_name -r preferred_list
[-a available_list] [-P TAF_policy]

srvctl start service -d database_unique_name [-s service_name_list] [-i inst_name]  [-o start_options]

srvctl stop service -d database_unique_name -s service_name_list [-i inst_name]  [-o start_options]

srvctl enable service -d database_unique_name -s service_name_list [-i inst_name]

srvctl disable service -d database_unique_name -s service_name_list [-i inst_name]

srvctl relocate service -d apps -s crm -i apps1 -t apps3

srvctl status service -d apps -s crm

srvctl config service -d apps -s crm -a

Example of Services and Thresholds Alerts

To check the thresholds for the payroll service, use the AWR report. You should record output from the report over several successive intervals during which time the system is running optimally. For example, assume that for an e-mail server, the AWR report runs each Monday during the peak usage times of 10:00 a.m. to 2:00 p.m. The AWR report would contain the response time, or DB time, and the CPU consumption time, or CPU time, for calls for each service. The AWR report would also provide a breakdown of the work done and the wait times that are contributing to the response times.

Using DBMS_MONITOR, set a warning threshold for the payroll service at 0.5 seconds and a critical threshold for the payroll service at 0.75 seconds. You must set these thresholds at all instances within an Oracle RAC database. You can schedule actions using Enterprise Manager jobs for alerts, or you can schedule actions to occur programmatically when the alert is received. In this example, thresholds are added for the servall service and set as follows:

EXECUTE DBMS_SERVER_ALERT.SET_THRESHOLD( 
METRICS_ID => DBMS_SERVER_ALERT.ELAPSED_TIME_PER_CALL 
, warning_operator => DBMS_SERVER_ALERT.OPERATOR_GE 
, warning_value => '500000' 
, critical_operator => DBMS_SERVER_ALERT.OPERATOR_GE 
, critical_value => '750000' 
, observation_period => 30 
, consecutive_occurrences => 5 
, instance_name => NULL 
, object_type => DBMS_SERVER_ALERT.OBJECT_TYPE_SERVICE 
, object_name => 'servall');

Verify the threshold configuration using the following SELECT statement:

SELECT METRICS_NAME, INSTANCE_NAME, WARNING_VALUE, CRITICAL_VALUE, 
OBSERVATION_PERIOD FROM dba_thresholds ;

Enable Service, Module, and Action Monitoring

You can enable performance data tracing for important modules and actions within each service. The performance statistics are available in the V$SERV_MOD_ACT_STATS view. As an example, set the following:

• Under the ERP service, enable monitoring for the exceptions pay action in the payroll module.

• Under the ERP service, enable monitoring for the all actions in the payroll module.

• Under the HOT_BATCH service, enable monitoring for all actions in the posting module.

EXECUTE DBMS_MONITOR.SERV_MOD_ACT_STAT_ENABLE(service_name => 'erp', module_name=>
 'payroll', action_name => 'exceptions pay');
EXECUTE DBMS_MONITOR.SERV_MOD_ACT_STAT_ENABLE(service_name => 'erp', module_name=>
 'payroll', action_name => NULL);
EXECUTE DBMS_MONITOR.SERV_MOD_ACT_STAT_ENABLE(service_name => 'hot_batch', 
module_name =>'posting', action_name => NULL); 

Verify the enabled service, module, action configuration with the following SELECT statement:

COLUMN AGGREGATION_TYPE FORMAT A21 TRUNCATED HEADING 'AGGREGATION'
COLUMN PRIMARY_ID FORMAT A20 TRUNCATED HEADING 'SERVICE'
COLUMN QUALIFIER_ID1 FORMAT A20 TRUNCATED HEADING 'MODULE'
COLUMN QUALIFIER_ID2 FORMAT A20 TRUNCATED HEADING 'ACTION'
SELECT * FROM DBA_ENABLED_AGGREGATIONS ; 

The output might appear as follows:

AGGREGATION            SERVICE                MODULE        ACTION
------------           --------------------   ----------    -------------
SERVICE_MODULE_ACTION  ERP                    PAYROLL       EXCEPTIONS PAY
SERVICE_MODULE_ACTION  ERP                    PAYROLL
SERVICE_MODULE_ACTION  HOT_BATCH              POSTING