UltraLite database schema

The logical framework of the database is known as a schema. In UltraLite, the schema is maintained as a catalog of system tables that hold the metadata for the UltraLite database. Metadata stored in the system tables includes:

Index definitions. See sysindex system table and sysixcol system table.
Table definitions. See systable system table.
Column definitions. See syscolumn system table.
Publication definitions. See syspublication system table and sysarticle system table.
User names and passwords. See sysuldata system table.

Schema changes with DDL statements

You can change the schema of a database with the appropriate Data Definition Language (DDL) statements or by using the ALTER DATABASE SCHEMA FROM FILE statement to modify the schema definition using a SQL script.

Schema changes can take a considerable amount of time. For example, all rows in the associated table must be updated when the column type is changed. DDL statements successfully execute when there are not any:

Uncommitted transactions.
Other active uses of the database (for example, synchronization, prepared but unreleased statements, or executing database operations).

When the DDL statement is executing, any other attempt to use the database is blocked until the DDL statement completes the schema change.

UltraLite database schema

Schema changes with DDL statements

See also