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# SQL Server Index Maintenance: Rebuild vs Reorganize
Indexes can make SQL Server queries dramatically faster, but indexes also require maintenance as data changes. Two commonly discussed operations are **reorganize** and **rebuild**.
## What is fragmentation?
When rows and index pages change over time, the logical order of index pages can become less efficient. Fragmentation is one factor that may affect workloads that depend heavily on ordered index scans.
Do not treat fragmentation percentage as an automatic command to rebuild every index. Query workload, index size, storage, and SQL Server version all matter.
## Reorganize
Reorganizing an index is an incremental operation and is generally less disruptive than a rebuild. A typical command is:
```sql
ALTER INDEX IX_Orders_OrderDate
ON dbo.Orders
REORGANIZE;
```
## Rebuild
A rebuild recreates the index:
```sql
ALTER INDEX IX_Orders_OrderDate
ON dbo.Orders
REBUILD;
```
A rebuild can consume more CPU, memory, I/O, and transaction-log resources, so schedule maintenance appropriately.
## Check fragmentation
You can inspect index statistics with `sys.dm_db_index_physical_stats`:
```sql
SELECT
OBJECT_NAME(object_id) AS TableName,
index_id,
avg_fragmentation_in_percent,
page_count
FROM sys.dm_db_index_physical_stats(
DB_ID(), NULL, NULL, NULL, 'LIMITED');
```
Use the results as one input into a maintenance strategy rather than blindly applying a fixed fragmentation threshold to every index.
## Practical approach
For a production database, consider:
1. Identify large, frequently used indexes.
2. Measure fragmentation and page counts.
3. Check query performance before changing maintenance.
4. Reorganize or rebuild based on the workload and operational requirements.
5. Monitor duration, blocking, CPU, I/O, and log growth.
## Summary
Index maintenance should be workload-driven. Reorganize is generally an incremental operation, while rebuild recreates the index and can be more resource-intensive. Measure first, then choose the operation that makes sense for the database.
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