ORA-55746
Reservable column update statement only supports + or - operations on a reservable column.
Cause
An attempt is being made to update a reservable column with something other than a + or -. An amount should be added or subtracted from the reservable column. Direct assignments to reservable columns are not supported.
Action
Change the update statement to add or subtract from the same reservable column. The set clause should be of the form reservable_col1 = reservable_col1 + (expression) or reservable_col1 = reservable_col1 - (expression)." where the expression in parenthesis evaluates to the amount to be added or subtracted from the same reservable column, reservable_col1.