From phpBB Development Wiki
Currently schema changes must be made in:
- create schema files script - this updates schema .sql files in install
- database updater
Data changes go into schema_data and in the data area of database updater.
Whenever a new version is started, it must be added to database updater in two places. One for schema and the other one for data.
Sometimes it is necessary to change schema, then alter some data and then perform more schema changes. This is accomplished by manually invoking make schema changes function from the data modification part in database updater.
The operations that database updater can be performed are defined in db_tools, which is in includes/db. This file is copied into install directory during package building.