Each table and each index on a table has an object allocation map (OAM). A single OAM page holds allocation mapping for between 2,000 and 63,750 data pages or index pages. In most cases, the number of OAM pages required is close to the minimum value. To calculate the number of OAM pages for the table, use:
Formula 
Example 


Number of reserved data pages / 63,750 
= 
Minimum OAM pages 
750,000 / 63,750 
= 
12 
Number of reserved data pages / 2000 
= 
Maximum OAM pages 
750,000 / 2000 
= 
376 
To calculate the number of OAM pages for the index, use:
Formula 
Example 


Number of reserved index pages / 63,750 
= 
Minimum OAM pages 
3396/ 63,750 
= 
1 
Number of reserved index pages / 2000 
= 
Maximum OAM pages 
3396 / 2000 
= 
2 
Finally, add the number of OAM pages to the earlier totals to determine the total number of pages required:
Formula 
Example 


Minimum 
Maximum 
Minimum 
Maximum 

Clustered index pages 
3396 
3379 

OAM pages 
+ 
+ 
1 
2 
Data pages 
+ 
+ 
750000 
750000 
OAM pages 
+ 
+ 
12 
376 
Total 
753409 
753773 