Application packager may include a special script into the package that serves for backing up application user data and further its restoration on new application instance in case of some failures, updates or migration. These operations are performed with the help of backup script on application 'root' service instance. Migration operation is a sequential execution of backing up and restoring operations in this regard.
The backup script is declared with the "//service/provision/backup-script" element defined by the Specification in section 5.3.5. Backup/Restore Script. Its declaration must include programming language it is written in. The script is invoked on instance backing up or restoring.
The details of Controller behavior specific for invoking backup script during a particular operation are considered further in this section.