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

Working With Vartables
Advanced NCL Programming
106160 Tandem Computers Incorporated 18–25
For vartables defined with a value of LIMIT greater than zero (0), this operand
indicates whether VARTABLE ADD and VARTABLE PUT can delete the oldest entry
automatically when the table is full.
Key Characteristics
Keys uniquely identify entries. Every entry in a vartable has a key. There are two
operands you can use with the VARTABLE ALLOC verb to specify the key
characteristics—KEYFMT and KEYLEN.
Format, specified by KEYFMT, determines whether the table has numeric or string
type keys.
Length, specified by KEYLEN, determines the length of string type keys. This can
range from 1 through 256 characters long. Each table you create can have a different
key length, but is padded with blanks to the defined length.
Maximum Number of Entries
You can explicitly specify a maximum number of entries in a vartable using the LIMIT
operand of the VARTABLE ALLOC verb. The maximum number of entries is
1,000,000. A value of 0 means that the number of entries is unlimited.
Counter Characteristics
Entries have two counter fields. The first is a system-maintained counter field, which
is initialized to 0 (zero) when an entry is created and can be reset to any value or
adjusted by any amount on update calls.
The second is called a user correlator field. This field is maintained by the system and
may be used to provide update synchronization for tables shared between NCL
processes, that is, for tables with region-wide or global scope.
The entries in a table are maintained in ascending key field value order. The retrieval
option of the VARTABLE GET verb allows sequential retrieval in ascending or
descending order.