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 |
