Sybase DC38133-01-0902-01 Publication design for Adaptive Server Anywhere, Design issues overview

Publication design for Adaptive Server Anywhere

Once you understand how to create simple publications, you must think about proper publication design. Sound design is an important part of building a successful SQL Remote installation. This section helps set out the principles of sound design as they apply to SQL Remote for Adaptive Server Anywhere.

Similar material for Adaptive Server Enterprise

Many of the principles of publication design are the same for Adaptive Server Anywhere and Adaptive Server Enterprise, but there are differences in commands and capabilities. There is a large overlap between this section and the corresponding section for Adaptive Server Enterprise users, “Publication design for Adaptive Server Enterprise” on page 147 .

Design issues overview

Each subscription must be a complete relational database

Transaction integrity must be maintained in the absence of locking

A remote database shares with the consolidated database the information in their subscriptions. The subscription is both a subset of the relational database held at the consolidated site, and also a complete relational database at the remote site. The information in the subscription is therefore subject to the same rules as any other relational database:

♦ Foreign key relationships must be valid For every entry in a foreign key, a corresponding primary key entry must exist in the database.

The database extraction utility ensures that the CREATE TABLE statements for remote databases do not have foreign keys defined to tables that do not exist remotely.

♦ Primary key uniqueness must be maintained There is no way of checking what new rows have been entered at other sites, but not yet replicated. The design must prevent users at different sites adding rows with identical primary key values, as this would lead to conflicts when the rows are replicated to the consolidated database.

The data in the dispersed database (which consists of the consolidated database and all remote databases) must maintain its integrity in the face of updates at all sites, even though there is no system-wide locking mechanism for any particular row.

♦ Locking conflicts must be prevented or resolved In a SQL Remote installation, there is no method for locking rows across all databases to prevent different users from altering the rows at the same time. Such conflicts must be prevented by designing them out of the system or must be resolved in an appropriate manner at the consolidated database.

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