SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Managing an SQL/MX Distributed Database
HP NonStop SQL/MX Installation and Management Guide—523723-004
13-5
SQL/MX Distributed Database Features
When you register a catalog from the local node to remote nodes, you ensure that the
catalog’s database objects can be successfully resolved to corresponding underlying
Guardian file names when accessed by their ANSI names on remote nodes. Similarly,
the metadata definitions for a database object, identified by its ANSI name, can be
located and retrieved regardless of where that database object's metadata definitions
are located in the network.
For location-independent ANSI names, ANSI name lookup always starts with the
CATSYS and SCHEMATA system schema tables on the local node. Next, the node
that contains the metadata definitions for the ANSI-named object is identified. For
Release 2.1 or Release 2.0, that node must have the automatic catalog reference for
the object's catalog. The location of the node can be identified from the
CAT_REFERENCES table of the system schema of any node on which the object’s
catalog is registered. The remainder of the lookup involves using the catalog’s
definition schema tables on the automatic catalog reference node.
Visibility Rules
Distributed database objects can be accessed from a node only if the objects are
visible on that node.
For Release 2.1 or Release 2.0, these visibility rules govern all access to database
objects and metadata in a distributed database environment:
•
A database object on one node is visible on a remote node only if a catalog
reference for the object’s catalog has been registered on that node. The affected
catalog, including all schemas and database objects within it, is then visible from
that node.
•
A database object can be distributed only to remote nodes where its catalog has
been registered.
•
A database object—or a partition of the object—can be opened only if that object’s
catalog is visible on both the local node and the node where the object or partition
resides.
•
To avoid visibility anomalies, related catalogs must have identical visibility. This rule
affects statements or commands that establish a relationship between catalogs,
such as a CREATE VIEW statement that references tables from two or more
catalogs in the view’s query text.
Although their names are similar to ANSI names, the compiled modules in OSS
directories are not subject to these visibility rules.
Transparency
The use of distributed databases is transparent to users and applications except for
statements, commands, and syntax that directly manage the distribution. When the
objects in a user catalog created on one node are visible to other nodes, there are no
limitations on what those other nodes can do with the catalog’s objects. The other