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

Opening a UDB or UDB Pair for Access by NCL
Working With Files
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Specifying Record
Structure
When you open a UDB or UDB pair using the FILE OPEN verb, you can specify to
NCL how the data is physically organized in each UDB record by using the FORMAT
operand. This determines how NCL interprets data when it reads a record from a
UDB or UDB pair and writes a record to a UDB or UDB pair.
Data in a UDB record can be physically organized in three different formats. These
formats are called:
Mapped
Unmapped
Delimited
The corresponding UDBs are called mapped UDBs, unmapped UDBs, and delimited
UDBs.
The Structure of a Mapped UDB
In a UDB where data is mapped, components of the map describe the length of the
data in a record and the length of the data in the fields. NCL uses Mapping Services to
process records in mapped UDBs.
The default map used by NCL to interpret records in a mapped UDB is $NCL,
although you can specify other maps, such as $MSG, $SEC, or a user-defined map, if
you wish.
The map $MSG is used when you are working with messages. The activity log is an
example of a UDB that contains records that Mapping Services can interpret using the
map $MSG.
The map $SEC is used when you are working with user ID definition records. The
User ID Management Services (UMS) database is an example of a UDB that contains
records that Mapping Services can interpret using the map $SEC. (The FILE verbs,
however, cannot access the data in the UMS database; you must use the SECCALL
verbs to do this.)
You would use a user-defined map to read records from and write records to an
Enscribe file that is created by an external application, or to write records to a new
Enscribe file created by NonStop NET/MASTER MS for later access by an external
application. A user-defined map allows an NCL process and an external application
to share access to data in the same Enscribe file.
How to read records from a mapped UDB and write records to a mapped UDB is
discussed in more detail later in this section. See Section 10, "Working With Mapping
Services," for more information on Mapping Services. Section 11, "Standard and
User-Defined Maps," discusses the structure of the maps $MSG, $NCL, and $SEC, and
how to create and use a user-defined map.