RDBMS Vendor

Choosing an RDBMS Vendor

You'd think that it wouldn't matter which RDBMS you use behind a Web site because every RDBMS comes with a standard SQL front end. In fact the vendors' flavors of SQL are different enough that porting from one RDBMS to another is generally a nightmare. Plan to live with your choice for 5 or 10 years.

Here are some factors that are important in choosing an RDBMS to sit behind a Web site:

1. cost/complexity to administer
2. lock management system
3. full-text indexing option
4. maximum length of VARCHAR data type
5. support

Cost/Complexity to Administer

In the bad old days you might install Oracle on a $500,000 computer and accept all the defaults, then find that the rollback segment was about 15 MB. That means that you couldn't do a transaction updating more than 15 MB of data at a time on a computer with 200 GB of free disk space. Oracle would not, by default, just grab some more disk space. Sloppy RDBMS administration is one of the most common causes of downtime at sophisticated sites. If you aren't sure that you'll have an experienced staff of database administrators to devote to your site, then you might want to consider whether an "Enterprise RDBMS" is really for you. The Big Three RDBMSes are IBM's DB2, Microsoft SQL Server, and Oracle. All offer tremendous flexibility in configuration with an eye towards building 64-CPU systems that process absurd numbers of simultaneous transactions. All claim that their latest and greatest management tools make installing and administering the system is so easy a 10-year-old could do it. If these claims were true the local Starbucks would be clogged with unemployed database administrators. Midget competition is provided by the open-source PostgreSQL, which can't be scaled up to the large sizes and performance of the commercial RDBMSes but is inherently fairly simple to install and maintain (and it is free!). MySQL is popular among Linux users and because it has a SQL front-end it is often confused with an RDBMS. In fact it does not provide the ACID transaction guarantees and therefore would more properly be lumped in with Microsoft Access and similar desktop tools.