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1.3 Why should I care about SQL tables?
Key points
- You may not need to care. Don't waste your time reading this document if
you have already decided you will only use IMAGE/SQL and some off-the-shelf
SQL decision support tool (such as Information Access by Hewlett-Packard)
to access your existing TurboIMAGE data sets in "read-only" mode.
If you don't insert data into the SQL side (either the system catalog or
user tables), then you don't need to worry about SQL storage management or
concurrency issues (except at IMAGESQL ATTACH and DETACH time).
You might want to read Chapter 3 to learn more
about SQL security, however, as future enhancements to IMAGE/SQL security
may take advantage of the SQL approach.
- You may be considering evolving your existing TurboIMAGE applications to SQL
because it is "open":
"[IMAGE/SQL] is a superb migration tool, which will allow users to develop
new applications on a true fully-featured relational database (ALLBASE/SQL),
while still accessing the data held in IMAGE legacy applications. This
means a migration that once looked unavoidable and daunting suddenly can be
carried out little by little, over several years, to suit your company's
convenience ... HP has pulled off its biggest coup since Compatibility Mode
gave us painless migration to PA-RISC."
Martin Knapp, PROACTIVE SYSTEMS SENIOR SOFTWARE ENGINEER
Reprinted from the December, 1994 edition of InterexPress.
ALLBASE/SQL is available on both the HP3000 and the HP9000. In addition,
ALLBASE/SQL adheres to industry SQL standards, which means you can eventually
"migrate" to another SQL vendor (and hardware platform) if you ever
want to.
- You may be considering evolving to SQL because of the benefits of using a
relational model instead of a network model:
- Client/Server development tools.
- The DBA has more flexibility to make database changes. Programs don't
"break" when changes are made because they don't have intimate
knowledge about how data is physically stored.
- If you decide to develop an SQL application that will access the data in your
TurboIMAGE database, you will probably insert compiled SQL statements (known
as stored sections) into the system catalog (a special set of SQL tables).
The system catalog serves essentially the same function as the root file (it
contains metadata about each of the objects in the DBEnvironment). SQLCORE
accesses information in the system catalog when it executes most SQL
statements. Locks are acquired during this process, which can result in
concurrency problems if you are not aware of the issues.
- And finally, you may want to create an SQL table instead of creating a new
data set in a TurboIMAGE schema.
Page last updated on November 29, 1995
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