There is some confusion surrounding the meaning of the values
in PROMON: Database Status for:
- Total number of database blocks
- Database blocks high water mark
Total number of database blocks is equal to the physical database size. This number is reported in blocks, and needs to be multiplied by the database block size to determine the physical database size in bytes.
Database blocks high water mark is equal to the largest number of database blocks that contained data since the creation of the database. It is the pointer between the data/index information in the database and the Free Chain which is a list of empty blocks waiting to be allocated as index or data information. In other words, the
Total number of database blocks will always be equal to or greater than the
high water mark.
More importantly, as for all the other metrics from this
PROMON > Database Status menu like
"Record blocks with free space" for example, these are 'database wide' metrics. These were valuable in the days when we had single extent/storage area databases.
With the introduction (and use) of Storage Areas, this information is no longer useful apart from the
Total number of database blocks providing an estimate of the current database size + bi extents. To to determine database occupation on a per Storage Area basis using VST's, refer to the code example provided in Article:
