SQL/MX Queuing and Publish/Subscribe Services

Introduction
HP NonStop SQL/MX Queuing and Publish/Subscribe Services—523734-002
1-5
Concepts
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Enable the SQL compiler and SQL system to optimize access to queue entries,
notifications, and normal SQL data.
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Enable scalability and load distribution through horizontal partitioning and fault
tolerance through process pair technology.
Concepts
SQL/MX’s publish/subscribe extensions are based on three fundamental concepts:
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Streams. Applications perceive queues and channels as continuous data streams.
The stream access mode allows applications to access regular audited SQL tables
as continuous data streams.
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Destructive SELECTs. The possibility to embed DELETE and UPDATE statements
within FROM clauses allows applications to read and at the same time update or
delete rows in an SQL audited table.
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Skip conflict access. Transactional queuing services attempt to minimize conflicts
between concurrent transactions by skipping entries locked by concurrent
transactions. The skip conflict access mode allows transactions to skip rows locked
in a conflicting mode.
Support for SQL/MP and SQL/MX Tables
Publish/subscribe services work the same on SQL/MP- and SQL/MX-format tables.
Unless otherwise indicated, the functional descriptions in this manual apply to both
types of tables. The examples in this manual use ANSI names but are otherwise
identical to examples using Guardian names.
Major Features
The extensions for queuing and publish/subscribe services are provided through
access modes, SQL language extensions, and SQL run-time extensions. The major
features enabled by these extensions are listed here and described in more detail in
Section 2, Major Queuing Features:
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Stream access mode
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Embedded DELETE and UPDATE statements
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Skip conflict access mode
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Set on rollback
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Holdable cursors
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Rowset integration
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Horizontally partitioned tables
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Ordered streams