SharePoint Products and Technologies support large lists. However, you must carefully control how end-users view the lists to help prevent adverse effects on performance.
- For best performance, do not exceed 2,000 items in a list level (for example, the root of the list or a single folder).
- If you must create and browse large lists, use the following best practices:
- Index the list on one or more columns.
- Change the default view of the list to a customized filtered view that follows these recommendations
- The view returns fewer than 5,000 items
- The first column that you use to filter the view has an index and that it sufficiently reduces the total number of items returned.
- The view displays only those columns that are absolutely required.
- The view includes as few lookup columns as possible. Each lookup column in a list that is included in a view causes an additional join and additional calls to the database.
- Evaluate list size with regard to the number of columns in a list. Lists with lots of columns can perform slowly.
Be aware that the following settings and operations can significantly affect the performance of a site that has large lists.
- Complex explicit permissions (permissions on the list or library, folder, or item or document level) force authorization checking on each item.
- Changing authorization settings.
- Creating, updating, and deleting indexes.
- Importing and exporting content.
- Deleting a list.
- Deploying new content types or updating existing content types.
- If you have workflows that generate lots of task and history items, you might be creating large lists. For very active workflows, follow these practices:
- Keep the AutoCleanupDays timer job running to clean up tasks on completed workflows older than 60 days.
- When you create workflow associations, if you expect that a workflow will be heavily used or will create lots of task and history items, use non-default task and history lists.
Please be aware that if you have a site that uses large lists, it can slow down the performance of site collection backups performed with the Stsadm backup operations.