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
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Maintaining Local Autonomy in a Network
Users of a distributed node must have remote passwords for remote network access.
The access privileges assigned by GRANT to users for SQL/MX objects on the local
node also apply to those users when the objects are located on a remote node or are
accessed from a remote node to which a user has remote access authorization.
Maintaining Local Autonomy in a Network
In the context of a network distributed database, local autonomy ensures that a user
can access local data regardless of the availability of remote dependent objects. For
Release 2.1 or Release 2.0, these restrictions apply:
•
Dynamic DDL and DML operations must have access to object metadata. If the
node on which the object metadata is located becomes unavailable, other network
nodes cannot perform dynamically compiled DDL or DML operations on that object
data to any node.
•
To use late name resolution of ANSI names or automatic recompilation with static
DML operations, the object metadata must also be accessible. However, static
DML statements that do not use ANSI names, late name resolution of ANSI
names, or automatic recompilation can execute locally if the node on which the
object metadata is stored is not available.
•
For objects that are partitioned across network nodes, you cannot perform DDL
operations on any partitions in the network—even those on available nodes—if one
of the partitioned nodes becomes unavailable. For example, if a table is partitioned
across two nodes and one node goes down, the surviving node cannot drop the
partitioned table. The same is true of DML operations that use late name resolution
of ANSI names or automatic recompilation.
These SQL/MX operations require access to object metadata. Therefore, if the node
containing the object metadata is unavailable, you cannot perform these SQL/MX
operations on the associated object data from any network node:
•
DDL and utility operations (for example, CREATE TABLE, IMPORT, UPDATE
STATISTICS)
•
Dynamic compilation of DML queries (for example, SELECT, including queries
entered from MXCI and NonStop ODBC/MX)
•
Static compilation of modules
•
Run-time ANSI name resolution of DML queries (for example, queries that use
host variables and prototyping to specify the database object names at runtime)
•
Run-time automatic recompilation of DML queries
In a distributed database, statically-compiled queries can execute even if some of the
nodes in the database are not available, provided these two requirements are met:
•
Either the node that stores the query objects’ metadata is available, or the query
does not use late name resolution of ANSI names or automatic recompilation.