Defining a service policy

You can define service policies and, for most kinds of work requests, work classes to categorize and prioritize work requests. A service policy consists of a user-defined performance goal and an importance level, in some cases.

1. From the administrative console click Operational policies > Service policy. You can select an existing service policy to edit, or click New to create a service policy.
   To edit an existing service policy, click the service policy name.
2. Create a name, description, and a goal type for your new service policy.
   The goal type can be either discretionary, average response time, or percentile response time:

   • A discretionary goal is the default, and indicates work that does not have significant value. As a result, work of this type can see a degradation in performance when resources are constrained.
   • Average response time goals are indicative of work with a higher priority than discretionary. The average response time goal is assigned a specific time goal.
   • Percentile response time goals are another measure for work with a higher priority than discretionary. The percentile response goals are defined with specific criteria on the following panel. The percentile response time target is the percentage of requests whose response time is T or less that should be P or more; a target has particular values for T and P.
3. Optional: If you select a goal type of average response time, or percentile response time, you are prompted to define the specifics and select an importance.

   For average response time goals, type a goal value, associate an importance with the service policy, and select Monitor for persistent policy violations to set up the creation of a runtime task when a policy violation occurs.

   When you associate an importance with the service policy, the options for importance vary from lowest to highest. Some planning is essential to select the correct importance value, because negative results can occur if all work is rated as highest. This rating can create a bottleneck within the environment. To define a policy violation, specify the Goal delta value and the Time period value:

   • In the Goal delta value field, type an integer to indicate the maximum allowable amount of time that exceeds the configured goal value. Acceptable values are 0 to 3000 milliseconds, 0 to 300 seconds, and 0 to 2147483647 minutes.
   • In the Time period value field, type an integer to indicate the milliseconds, seconds, or minutes after which the goal value is in violation. This value can be 0 to 1 day, inclusive.

   For percentile response time, set the goal percentile to the percentage of requests that must meet the goal value that is defined in the next field. Next, type a goal value, associate an importance with the service policy, and select Monitor for persistent policy violations to set up the creation of a runtime task when a policy violation occurs.

   For the goal value, type the maximum allowable time for the service policy. The environment tries to stay beneath the defined goals, and continually adjusts to achieve the most balanced result. When you associate an importance with the service policy, the options for importance vary from lowest to highest. Some planning is essential to select the correct importance value; if all work is rated as highest, negative results can occur . To define a policy violation, specify the Goal delta percentage and the Time period value:

   • In the Goal delta value field, type an integer that indicates the percentage of request beneath the goal value for which to monitor. Acceptable values are 0 to 100, inclusive.
   • In the Time period value field, type an integer to indicate the milliseconds, seconds, or minutes after which the goal value is in violation.

   A runtime task is generated when certain criteria are violated. For example, in the following percentile response time example, with a percentile goal of 90% and a goal delta of 5%, the service policy is breached when less than 85% of requests meet the service time goal of 1 second (for 5 consecutive seconds), that is, when more than 15% of requests exceed the service time goal of 1 second (for 5 consecutive seconds). The system will still prioritize traffic in such a way as to attempt to meet the 90% goal, however no notification of a breach is issued unless the 85% (90% minus 5%) threshold is not met.

   Table 1. Percentile response time example

   Description	Value
   Goal percentile	90%
   Goal value	1
   Importance	1
   Monitor for persistent service policy violations	true
   Goal Delta Percentage:	5%
   Time Period Value	5 seconds

   For the goal value, type the maximum allowed time for the service policy. The environment continually adjusts all automatically adjustable controls, aiming to reach, and maintain the best possible balance of relative performance results. When you associate an importance with the service policy, the options for importance vary from lowest to highest. Some planning is essential to select the correct importance value; if all work is rated as highest, negative results can occur . This rating can create a bottleneck within the environment.

4. Associate transaction class members to the service policy, or create a transaction class.
   If the transaction class that you are seeking does not exist, create a transaction class.
5. To create a work class for your service policy, from the administrative console click Applications > Application types > WebSphere enterprise applications > application_name > Service policies. Select an existing service policy and for the request type, click New.

   To create a service policy for HTTP, specify a name for the work class, select a module, and select the members to add. Optionally, to use a custom URI, type its name, and click Add pattern in the Custom URI pattern field. For example, a custom URI is necessary to do JavaServer Pages (JSP) work.

   To create a service policy for SOAP, specify a name for the work class, select a module, and select the web service operations to add.

   To create a service policy for IIOP, specify a name for the work class, select a module, and select the EJB methods to add. Optionally, to use a custom EJB, type the information in the Custom EJB name and Custom EJB method fields, and click Add pattern.

   To create a service policy for JMS, type a name for the work class, select a module, select a defined bus, and select the EJB methods. Optionally, to use a custom bus, type the information in the Custom bus name and Custom bus destination fields, and click Add pattern.

   To create a service policy for SIP, you must create the following two policies:

   1. Create a default SIP policy with the following values:
      • Goal Type = Average Response Time
      • Goal Value = 75 milliseconds
      • Importance = High
   2. Create an INVITE policy with the following values:
      • Goal Type = Average Response Time
      • Goal Value = 75 milliseconds
      • Importance = Low
   3. Set the service policy SIP rules:
      • If request.method = INVITE, then classify to transaction class Default _TC_INVITE (INVITE).
      • If no rules apply, then classify to transaction class Default _TC_def_sip (def_sip).
6. The system automatically picks up any changes you make to your service policy configuration. You do not need to restart any servers when you update your service policies and work classes.