The logical framework of the database is known as a schema.
You can upgrade the schema of an UltraLite 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:
Other active uses of the database, such as 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.