The predefined Sort Overflows alarm becomes active when sorts have run out of sort heap and may have used disk space for temporary storage. There is an additional overhead cost when sorts overflow because the sort will need a merge phase. There is also the possibility of added I/O if the data does need to be written out to disk.
This alarm has been predefined with a Low severity level. The underlying metricfor this alarm can be adjusted to suit your environment by using the Metric Editor.
Try these performance turning methods:
At the database or application level—If sort overflows are high, try increasing the sort heap size.
At the statement level—SQL statements that require large sorts may benefit from further tuning to reduce the amount of sorting.