3.2. Notes about databases

Interchange maintains objects for all of its database tables defined in Database. These can be of diverse SQL, DBM, and LDAP types.

When the database is initialized at catalog configuration time, the individual database tables may be opened depending on type. In general, SQL and LDAP types are always opened, and DBM types are not.

Opening a database table can be expensive in terms of CPU and IO time. So when the database is opened for a page transaction, Interchange creates a "dummy" table object that waits for a real access. Those objects are trivial to create, and a fast processor can create hundreds of thousands per second.

When access is made, the database table is really opened and the expensive initialization is done. This allows many tables to be ready for access while only the ones used take up CPU and IO time.

Copyright 2002-2004 Interchange Development Group. Freely redistributable under terms of the GNU General Public License.