IMAGE/SQL: Reliable and Fast Database
IMAGE is the primary reason that the
a success. It is a reliable, simple, fast database for
After about a decade of enhancements it was renamed
TurboIMAGE, then TurboIMAGE/XL after the PA-RISC
Programs can access and update records using
Today it is known as IMAGE/SQL
because it includes an
(Structured Query Language) frontend and
client-server support for PC accessors.
- Use masters for unique data items like customer numbers.
- Use details for repeated data like customer purchases.
- If a master record needs an alternate key, make it a detail and use an automatic master.
- If the information in a detail dataset is volatile,
avoid more than two paths into
it, and avoid sorted paths,
except where entries are put in chain order.
Remember that IMAGE now allows any data-type as
a sort field (sort fields used to be limited to unsigned data-types).
If the information is relatively static and frequently
accessed by on-line users,
add more search paths into it.
for fast serial scans and eliminate infrequently used search keys.
Polishing Database Design
- For numeric fields, use J1 for fewer than five digits; use J2 for fewer than ten digits; otherwise, use a P-field (packed-decimal).
- Types X, U, P, and Z give the best hashing results, especially if the key length is greater than six bytes.
- Avoid keys of type I, J, K, and R.
- Store dates in yyyymmdd format, either as a J2 (32-bit integer) or as an Z8 (do not leave out the century).
- Assign a primary path to every detail dataset; select the most frequently used path with more than one entry per chain.
- Try to keep master datasets less than 80 percent full.
- Never use a power of 2 as a master capacity (for example, 32, 1024, and so on).
- Avoid tricky data structures that you cannot use in all your tools.