Enabling and Disabling the Index

 Disabling indexes during data loading can be beneficial in certain scenarios, especially when dealing with large volumes of data. Here are some considerations and best practices:

Benefits of Disabling Indexes During Data Loading

1. Improved Data Load Performance: When indexes are disabled, SQL Server does not need to update the indexes for each row inserted, which can significantly speed up the data loading process.
2. Reduced Log Space Usage: Disabling indexes can reduce the amount of transaction log space used during bulk inserts.

Drawbacks of Disabling Indexes During Data Loading

1. Post-Load Index Rebuild: After the data load, you will need to rebuild the indexes, which can be time-consuming and resource-intensive.
2. Temporary Lack of Index Benefits: While indexes are disabled, any queries running against the table will not benefit from the indexes, potentially leading to slower query performance.

Best Practices

1. Evaluate the Data Volume: For small to moderate data loads, the overhead of maintaining indexes might be acceptable. For large data loads, disabling indexes can provide significant performance benefits.
2. Monitor System Resources: Ensure that you have sufficient system resources (CPU, memory, disk I/O) to handle the index rebuild after the data load.
3. Schedule Maintenance Windows: Perform data loading and index maintenance during off-peak hours to minimize the impact on users and applications.

Disable the Index

ALTER INDEX IX_OrderDate_CustomerID
ON Orders
DISABLE;

Enable (Rebuild) the Index

ALTER INDEX IX_OrderDate_CustomerID
ON Orders
REBUILD;