ejb timer service DatabaseTimerPersistence currently use the same insert statement for interval timer, calendar timer, and auto timer. These 3 types of timers have different required columns, and so at runtime to insert a timer, some of these columns that do not apply for the current timer have to be set to null, to match the ? mark in the statement.

For interval time, none of the schedule related columns apply. So these 13 fields are set to null in the prepared statement.

We should consider using separate insert statement for different types of timers, and only include the relevant columns in the prepared statement.