Highwater Extent Resize

J

Jack@dba

Member
Hi All,

I like to know about High water extent resize.We are planning to monitor extent size growth on monthly basis and based on growth report we are planning to add new extents.

I have found program to monitor extent growth using following url.
Progress KB - Virtual System Table (VST) used to calculate database occupation

But in o/p it displaying highwater extent name.
Using _file list i able to get file id,filesize name.... etc but which extent it is i not able to get from _filelist table.

How to get the details of high water extent whether it is fixed or variable and any idea on monitoring extent growth using VST tables?

Thanks
Durgaprasad.
 
I think your focus on the "extent" is misplaced.

You cannot resize an extent. Except by backing up the db, creating a new empty db structure with resized extents, and then restoring. But that isn't really "resizing an extent".

You *can* add pre-allocated space to a storage area by adding one or more extents. If there is a variable extent you must first remove that extent (if it has not been used. If it was used then you can only fix its size to whatever the current size is and then add new extents. Which will leave you with a funny sized extent. Esthetically that's a bit ugly but it doesn't hurt anything.)

You want to be tracking the high water mark in the storage area. A storage area is composed of one or more extents. There is a HWM that is tracked for each storage area but no equivalent in the VSTs for individual extents (except by coincidence when an area has just one extent).

You could figure out which extent contains the current HWM by adding up extent sizes for the storage area from _filelist until the extent sizes > the HWM (or when you find a variable extent). But I'm not sure why you would care to know that. It seems rather meaningless to me.

If you are trying to ensure that your storage areas do not run out of space (or do not start using a variable length extent if you created one for the area) then you would usually establish some sort of threshold that you use to tell you it is time to add an extent. For instance you might decide that when a storage area reaches 80% of its allocated size then it is time to add a new extent. Or perhaps when the area only has 1GB of free space you add an extent.
 
You must log in or register to reply here.
Back
Top