NET/MASTER Network Control Language (NCL) Programmer's Guide

Development Considerations for System-Level NCL Procedures
Developing System-Level NCL Procedures
106160 Tandem Computers Incorporated 17–7
Development
Considerations for
System-Level NCL
Procedures
System-level NCL procedures are designed to perform tasks that are distinctly
different from those of other NCL procedures. No other NCL procedures can intercept
and process system-level message flows. Accordingly, system-level NCL procedures
have specific development considerations.
Message Profile Variables All messages that travel to, from, and within NonStop NET/MASTER MS have a
profile. The concept of a message profile embodies three ideas:
All messages have a consistent structure.
All messages can contain certain attributes.
An NCL process can obtain information about a message.
All Messages Have a Consistent Structure
All messages received by NonStop NET/MASTER MS and generated by NonStop
NET/MASTER MS have a consistent message structure. This allows an NCL
process—such as EMSPROC, LOGPROC, or MSGPROC—to analyze all messages
using a consistent set of criteria.
The consistent structure of a message is made up of components such as headers, data,
elements, groups, and fields. The maps $MSG and $SPI (if a message contains the
NonStop NET/MASTER MS equivalent of SPI tokens) are used to interpret the
structure of a message. Using these maps to interpret the structure of a message is
discussed in detail in Section 10, “Working with Mapping Services.”
All Messages Can Contain Certain Attributes
All messages received by NonStop NET/MASTER MS and generated by NonStop
NET/MASTER MS can contain certain attributes.
For example, if the message contains text, its display attributes determine how a
message is displayed—its color, highlighting, intensity, and so on. If the message is a
non-roll-delete (NRD) message, its NRD attributes determine its type—whether it is a
full non-roll-delete message or a non-roll-delete message with the OPER attribute. All
messages contain other attributes, such as date and time of origin, the user ID or the
NCL ID of the originator, and so on.
Determining the attributes of a message is discussed in Section 10, “Working With
Mapping Services.” Refer to the discussion of message profile variables in the NonStop
NET/MASTER NCL Reference Manual for information on the range of attributes that a
message can have.