In the system tables of a database, the database system stores information about database objects and their relationships to each other, database states, statistics, operation and settings.
The system tables are not maintained by database users. The database system itself checks whether the system tables are still up to date every time the database is started. If this is not the case, an automatic function ensures that the system tables are updated.
You nevertheless have the option of updating (loading) the system tables at any time without needing to restart the database, for example in order to restore inadvertently deleted system table entries.