Kbase P20370: Empty blocks value appears to freeze under prostrct statisti
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
3/18/2003 |
|
Status: Unverified
FACT(s) (Environment):
Compaq Tru64 UNIX 5.1A
FACT(s) (Environment):
Progress 9.1C
SYMPTOM(s):
Empty blocks value appears to freeze under prostrct statistics
Empty blocks value is not changing
FIX:
Sometimes when looking with prostrct statistics, it might appear that the empty blocks value is not changing.
Empty blocks are blocks that have never been used by the database. Empty blocks are created when database extents are allocated when a database is first created. These blocks are above the high-water mark and have to be formatted before they can be used.
Free blocks are blocks that have been formatted by the database and which are ready to be used or re-used. They are formatted blocks and below the high-water mark.
Based on various algorithms -
- when the database can't find any available free blocks, it will take empty blocks and format them to create free blocks ready for use. This will result in the number of empty blocks decreasing.
- when the database does find available free blocks, it will take these instead of empty blocks. Thus there will be no change in the number of empty blocks.
Free blocks (free formatted space within the database) are also created when records are updated or deleted. If enough free blocks are becoming available through updates and deletes, then the database won't change empty blocks into free blocks and the number of empty blocks will remain the same.
Thus it could be that the behaviour you saw only looked like the number of empty blocks freezing, but what was actually happening was that the database was finding enough free blocks and didn't have to touch empty blocks at all.
In such a situation the area highwater mark (seen with the VST field _AreaStatus-Hiwater) will also not change, since space within the database will be getting reused.