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

Working With Vartables
Advanced NCL Programming
18–24 106160 Tandem Computers Incorporated
Vartable Scope
Vartable scope determines the visibility of the vartable to NCL processes and NonStop
NET/MASTER MS users. It restricts the use of the vartable. Scope can be NCL
process-wide, region-wide, or global. Scope is assigned using the SCOPE operand of
the VARTABLE ALLOC verb.
Process-wide scope is the default. This indicates that the table is visible only to the
NCL process that creates it. The table is automatically freed when the NCL process
terminates, if not explicitly freed beforehand. Table names must be unique within the
same NCL process.
Region-wide scope indicates that the table is visible to all NCL processes in the same
region. For a real user, this means all NCL processes executing under the same user
ID. The table is automatically freed when the region terminates. For a real user, this is
when the user logs off. Table names must be unique within the same region. Different
regions can use different tables of the same name.
Global scope indicates the table is visible to all NCL processes in NonStop
NET/MASTER MS. The table is automatically deleted when NET/MASTER
terminates, if not explicitly freed beforehand. Table names must be unique within the
same NonStop NET/MASTER MS system.
Hint To improve the performance of NonStop NET/MASTER MS, minimize the use of global vartables.
Ageing Characteristics of Entries
You can specify the ageing characteristics of entries using the AGE operand of the
VARTABLE ALLOC verb.
Specifying the ageing characteristics of entries determines how entries are to be aged
when operations are performed on them. Ageing allows a vartable to be used as a
temporary storage area, to keep frequently referenced entries in the vartable, and to
allow possible automatic deletion of old entries.
This operand affects the operation of the VARTABLE ADD, VARTABLE GET,
VARTABLE PUT, and VARTABLE UPDATE verbs.
Maximum Number of Data Fields
You can specify the maximum number of data fields in an entry using the DATA
operand of the VARTABLE ALLOC verb.
You can specify a value from 1 through 16. Each item may be from 0 (null) through
256 characters long. The data value is null if no data is provided for an item when an
entry is added. In Figure 18-1, the maximum value of n in Data is 16.
Entry Deletion Option
You can specify an entry deletion option using the DELOLD operand of the
VARTABLE ALLOC verb.