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

Controlling Access to UDBs by NonStop NET/MASTER MS
Working With Files
12–10 106160 Tandem Computers Incorporated
Refer to the NonStop NET/MASTER MS Command Reference Manual for more
information on the OPSYS and STATUS commands.
Controlling Access to
UDBs by NonStop
NET/MASTER MS
After you have created a single UDB or the files in a UDB pair, you must prepare the
UDB or UDB pair for system-wide access—that is, prepare it for access by NonStop
NET/MASTER MS—before NCL can work with it. The UDBCTL commands control
system-wide access to a UDB or UDB pair. In particular, you must open a UDB or
UDB pair for system-wide access and assign it an identifier before an NCL process can
work with the UDB or UDB pair.
This subsection describes how to use the UDBCTL commands. Refer to the NonStop
NET/MASTER MS Command Reference Manual for the complete syntax of the UDBCTL
commands, as well as for additional examples.
Opening UDBs for Access
by NonStop NET/MASTER
MS
If you want to work with a single UDB or UDB pair from NonStop NET/MASTER MS,
you must prepare it by using the UDBCTL OPEN command. This command makes
the UDB or UDB pair known to NonStop NET/MASTER MS and opens the UDB or
UDB pair for system-wide access. You cannot access a UDB or UDB pair from an NCL
process unless it is known to NonStop NET/MASTER MS and open for system-wide
access.
Entering the following command from the OCS command input line opens a single
UDB for system-wide access:
UDBCTL OPEN=$DATA.SUBVOL.MYFILE
This example shows the simplest form of the UDBCTL command to open a single
UDB. This command opens MYFILE for use with NonStop NET/MASTER MS for
read and write access.
Entering the following command from the OCS command input line opens a UDB pair
for system-wide access:
UDBCTL OPEN=($DATA.SUBVOL.MYFILE1,$DATA.SUBVOL.MYFILE2)
This example shows the simplest form of the UDBCTL command to open a UDB pair.
This command opens both MYFILE1 and MYFILE2 for use with NonStop
NET/MASTER MS. The order in which the file names are specified is significant:
MYFILE1 (the first file) is opened for read and write access; MYFILE2 (the second file)
is opened for read-only access.
Additionally, the UDB and UDB pair are opened so that many NCL processes, when a
UDB identifier is subsequently assigned, can open the UDB or UDB pair, and so that
no Guardian process has exclusive use of the UDB or UDB pair.
Assigning an Identifier to a UDB or UDB Pair
When you open a UDB or UDB pair by using the UDBCTL OPEN command, you must
assign the UDB or UDB pair an identifier before NCL can work with it. This is called a
UDB identifier (UDB ID). The UDB ID is the logical name used by NCL processes to