Compute node

To configure access to a database from this node:

• On the Basic tab, specify in Data Source the name by which the appropriate database is known on the system on which this message flow is to run. The integration node connects to this database with user ID and password information that you have specified on the mqsicreatebroker, mqsichangebroker, or mqsisetdbparms command.

  On z/OS® systems, the integration node uses the integration node started task ID, or the user ID and password that were specified on the BIPSDBP mqsisetdbparms command in the customization data set <hlq>.SBIPPROC.

• Select the Transaction setting from the list. The values are:
  • Automatic (the default). The message flow, of which the Compute node is a part, is committed if it is successful. That is, the actions that you define in the ESQL module are performed on the message and it continues through the message flow. If the message flow fails, it is rolled back. If you choose Automatic, the ability to commit or roll back the action of the Compute node on the database depends on the success or failure of the entire message flow.
  • Commit. To commit the action of the Compute node on the database, irrespective of the success or failure of the message flow as a whole, select Commit. The database update is committed even if the message flow itself fails.

  The value that you choose is implemented for the one or more database tables that you have added; you cannot select a different value for each table.

• To treat database warning messages as errors and have the node propagate the output message to the Failure terminal, select Treat warnings as errors. The check box is cleared initially.

  When you select the check box, the node handles all positive return codes from the database as errors and generates exceptions in the same way as it does for the negative, or more serious, errors.

  If you do not select the check box, the node treats warnings as typical return codes, and does not raise any exceptions. The most significant warning raised is not found, which can be handled as a typical return code safely in most circumstances.

• To force the integration node to generate an exception when a database error is detected, select Throw exception on database error. The check box is selected initially.

  If you clear the check box, you must include ESQL to check for any database error that might be returned after each database call that you make (you can use SQLCODE and SQLSTATE to do this). If an error occurs, you must handle the error in the message flow to ensure the integrity of the integration node and the database; the error is ignored if you do not handle it through your own processing because you have chosen not to invoke the default error handling by the integration node. For example, you can include the ESQL THROW statement to throw an exception in this node, or you can use the Throw node to generate your own exception at a later point in the message flow.

You can also automatically configure connectivity to a database by using the Database Service. For more information, see Database Service.

Code ESQL statements to customize the behavior of the Compute node. For example, you can customize the node to create a new output message or messages, using input message or database content (unchanged or modified), or new data. For example, you might want to modify a value in the input message by adding a value from a database, and storing the result in a field in the output message. By default, ESQL files are deployed as individual resources, and can be edited and redeployed without redeploying the message flows that reference them. For more information, see Deploying an ESQL file.

Code the ESQL statements that you want in an ESQL file that is associated with the message flow in which you have included this instance of the Compute node. The ESQL file, which by default has the name <message_flow_name>_<compute_node_name>.esql, contains ESQL for every node in the message flow that requires it. Each portion of code that is related to a specific node is known as a module.

If an ESQL file does not already exist for this message flow, double-click the Compute node, or right-click the node and click Open ESQL. This action creates and opens a new ESQL file in the ESQL editor view. If you prefer, you can open the appropriate ESQL file in the Application Development view and select this node in the Outline view.

If the file exists already, click Browse beside the ESQL Module property to display the Module Selection dialog box, which lists the available Compute node modules defined in the ESQL files that are accessible by this message flow (ESQL files can be defined in other, dependent, projects). Select the appropriate module and click OK. If no suitable modules are available, the list is empty.

If the module that you have specified does not exist, it is created for you and the editor displays it. If the file and the module exist already, the editor highlights the correct module.

If a module skeleton is created for this node in a new or existing ESQL file, it consists of the following ESQL. The default module name is shown in this example:

CREATE COMPUTE MODULE <flow_name>_Compute
       CREATE FUNCTION Main() RETURNS BOOLEAN
       BEGIN
              -- CALL CopyMessageHeaders();
              -- CALL CopyEntireMessage();
              RETURN TRUE;
       END;

       CREATE PROCEDURE CopyMessageHeaders() BEGIN
              DECLARE I INTEGER 1;
              DECLARE J INTEGER CARDINALITY(InputRoot.*[]);
              WHILE I < J DO
                     SET OutputRoot.*[I] = InputRoot.*[I];
                     SET I = I + 1;
              END WHILE;
       END;

       CREATE PROCEDURE CopyEntireMessage() BEGIN
              SET OutputRoot = InputRoot;
       END;
END MODULE;

If you create your own ESQL module, you must create this skeleton exactly as shown except for the procedure calls and definitions (described later in this section). You can change the default name, but ensure that the name you specify matches the name of the corresponding node property ESQL Module. If you want the module name to include one or more spaces, enclose the name in double quotation marks in the ESQL Module property.

Add your own ESQL to customize this node after the BEGIN statement that follows CREATE FUNCTION, and before RETURN TRUE. You can use the two calls included in the skeleton, to procedures CopyEntireMessage and CopyMessageHeaders.

These procedures, defined following function Main, provide common functions that you might want when you manipulate messages. The calls in the skeleton are commented out; remove the comment markers if you want to use the procedure. If you do not want to use a procedure, remove both the call and the procedure definition from the module.

The Compute Mode property controls which components are used by default in the output message. Select the property to specify whether the Message, LocalEnvironment (previously specified as DestinationList), and Exception List components that are either generated in the node or contained in the incoming message are used.

This default value is used when the transformed message is routed to the Out terminal when processing in the node is completed. The default value is also used whenever a PROPAGATE statement does not specify the composition of its output message.

Those components that are not included in your selection are passed on unchanged; even if you modify those components, the updates are local to this node.

Conversely, those components that are included in the selection are not passed on and the updates that are made in the node persist.

The value of the Compute Mode property specifies which new message trees are propagated from the Compute node. Therefore, for those message trees that are selected, the input messages are discarded unless they are explicitly copied into the new equivalent output message tree.

If All is selected, the Compute node is expecting to generate all three new message trees for the Root, LocalEnvironment, and ExceptionList by populating the OutputRoot, OutputLocalEnvironment, and OutputExceptionList. The input message trees are not passed to the output unless they are copied explicitly from the Input to the Output.

  SET OutputRoot = InputRoot;
  SET OutputLocalEnvironment = InputLocalEnvironment;
  SET OutputExceptionList = InputExceptionList;

To produce a new or changed output message, and propagate the same LocalEnvironment and ExceptionList, set the Compute Mode property to Message so that the LocalEnvironment and ExceptionList that are passed to the Compute or Mapping node, are passed on from the Compute node.

The Compute Mode applies only to propagation from the node. You can create all three output trees in a Compute or Mapping node and these can be manipulated and exist in the node. However, the Compute Mode determines whether such output trees are used on propagation from the node.

Where an output tree is named, ESQL creates this message tree before propagation. If your ESQL does not create the tree, no tree is propagated for that correlation name, and the input tree is not used in its place because the Compute Mode property did not indicate this option. Therefore, dependent on Compute Mode property settings and your ESQL, you might delete a tree that was input to the node, because you did not transfer it to the output tree, or propagate a changed tree as you intended.

The converse is also true. If your ESQL interrogates the input trees and does not need to propagate these trees, the Compute Mode property value might mean that the message tree propagates when you do not intend it to. For example, you might not want to propagate the LocalEnvironment and ExceptionList from a Compute node, but because you selected Message, the input versions of the trees are propagated. Even if the ESQL explicitly deletes the OutputLocalEnvironment and OutputExceptionList, these changes are local to that node because the Compute Mode property setting causes the input trees to be propagated.

The Environment component of the message tree is not affected by the Compute Mode property setting. Its contents, if any, are passed on from this node in the output message.

Set this property to reflect the output message format that you require. If you select an option (or accept the default value) that does not include a particular part of the message, that part of the message is not included in any output message that is constructed.

The Compute node has both an input and output message, so that you can use ESQL to refer to fields in either message. You can also work with both InputLocalEnvironment and OutputLocalEnvironment, and InputExceptionList and OutputExceptionList, as well as the input and output message bodies.

Set the validation properties to define how the message that is produced by the Compute node is to be validated. These properties do not cause the input message to be validated. It is expected that, if such validation is required, the validation has already been performed by the input node or a preceding validation node.

For more details, see Validating messages and Validation properties.