# Step 6: Calculate allocation overhead and total pages

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

## Total pages needed

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