Extents DB_AreaSpaceUtilizationHigh alert

DB_AreaSpaceUtilizationHigh Alert is being thrown every poll.
Monitoring concern as the database status in OE Management is Red due to the DB_AreaSpaceUtilizationHigh alerts.
Adding another variable extent fixes the current variable extent and continues to throw the DB_AreaSpaceUtilizationHigh alert.

High Water Mark (HWM) is in the variable extent.

The fact that the DB_AreaSpaceUtilizationHigh alert continues to be thrown after adding another variable extent to the area, is not because only the variable extent monitored.

The 9531 message for the DB_AreaSpaceUtilizationHigh Alert is essentially the same as would be found using the VST table:
_AreaStatus => 100 * (_AreaStatus-Totblocks - _AreaStatus-HiWater - _AreaStatus-Freeblks) / _AreaStatus-Totblocks. 
This information is available in the trend database in Db_AreaStatus.

So whenever data is growing into a variable extent, the alert is going to be triggered for ever Poll interval the Alert has been configured to do so, because the TOTAL BLOCKS is continually been extended in the variable extent and the HWM raised accordingly.

The only time you've really got to start worrying about this DB_AreaSpaceUtilizationHigh alert is if the Area in the alert is a TYPE I Storage Area, then it's down to the interpretation of percentages.

While this DB_AreaSpaceUtilizationHigh alert is simply saying that the HWM has breached x% of the total blocks,
For TYPE I Storage Areas, you need be aware of the maxarea limit being approached (viz with a 4KB blocksize, that would be 256 GB for 32 rpb, 128 GB for 64 rpb, 64 GB for 128 rpb etc). 

Otherwise, this DB_AreaSpaceUtilizationHigh alert is best useful when you ensure that it is acted upon before the variable extent is started to be used and add more FIXED extents + variable extent to accommodate anticipated growth, in order to raise the TOTAL BLOCKS.  As a PERCENTAGE, the larger the area grows, the more free blocks need to be added in order for there to be a significant difference to halt the alert from being thrown.  An alternative solution would be to turn off the alert and monitor the filesystem instead.