List Service Procedure Interface › List Service Procedures

List Service Procedures

A list service procedure interface is available for Common Application Services (CAS) lists.

List service procedures are installation-written NCL procedures that are available for performing specialized processing on lists.

A list service procedure must be present for the CAS list component to work. You specify the list service procedure when you define a list.

CAS executes the list service procedure at the following processing points:

• On initial entry to the list—&$LHOPT=INIT
• To retrieve a list entry—&$LHOPT=GET
• To process an action against a selected entry—&$LHOPT=ACTION
• To process an add request—&$LHOPT=ADD
• To process the ALL command—&$LHOPT=ALL
• Prior to terminating the list—&$LHOPT=TERM
• To process a command not recognized by CAS—&$LHOPT=COMMAND

You write your own list service procedures by using the variables described in the following sections.

The variables can be divided into the following groups:

• The first group of variables provide information to the procedure and are not modifiable (read-only). In particular, check the value of &$LHOPT to determine the stage of list processing for you to implement the required special processing.
• The second group of variables are modifiable and enable the procedure to return information to the system. Some of these variables are set with values already, but the procedure can change those values.

You can use your own variables in the list exit procedure. However, do not use variable names that start with #LH. The list service procedure is called with NOSHRVARS=(#LH). Once you specify your own variables, these variables are persistent through the different stages of list processing. That is, if you specify &A = variable_value, the value of this variable is available on each subsequent call to the procedure.