SQL/MX 3.2.1 Management Manual (H06.26+, J06.15+)

For more information, see “Planning Database Security and Recovery” (page 42).
SQL/MX Database Features
The SQL/MX RDBMS supports these features:
• “Distributed Databases” (page 19)
• “Database Protection and Recovery” (page 19)
• “Data Integrity” (page 20)
• “Multiple Character Sets” (page 21)
• “Database Security” (page 21)
• “Parallel Processing” (page 21)
• “High Availability” (page 22)
Distributed Databases
An SQL/MX database distributed across multiple nodes in an Expand network provides a high
level of transparency, location independence, read and update capability, and data integrity.
Objects in the same database can reside on different compatible nodes. The partitions of a table
or index can also be spread across compatible nodes.
A distributed database can be managed by a central site, by each independent distributed site,
or by a combination of these.
For SQL/MX distributed databases with SQL/MX tables, local autonomy is limited because of the
absence of true metadata replication from local to remote nodes. As such, local node autonomy
is confined to local data whose metadata exists on the local node.
For more information, see “Managing an SQL/MX Distributed Database” (page 266).
Database Protection and Recovery
An SQL/MX database is protected by:
• The HP NonStop Transaction Management Facility (TMF), which audits database changes
and provides automatic recovery.
TMF provides automatic online recovery of audited SQL/MX objects and files by using audit
trails. A transaction currently in progress can be aborted if a failure or error condition is
detected. TMF terminates the transaction and restores the database to its state before the
beginning of the transaction. TMF provides two additional recovery mechanisms:
◦ Volume recovery, which recovers the database in the event of a disk crash or system
failure.
◦ File recovery, which reconstructs specific audited files when the current copies on the
data volume are not usable (for example, if a system or media failure jeopardizes the
consistency of one or more audited files).
• The HP NonStop Remote Database Facility (RDF), which monitors changes made to a production
database on a local (primary) system and maintains a copy of that database on a remote
(backup) system.
The RDF subsystem enables you to use the backup database as a read-only resource to balance
the overall workload and improve response times. Activities at the backup system can include
querying the database, processing heavy batch-reporting loads, and consolidating data from
SQL/MX Database Features 19