When should I reindex SQL Server?

How often should you reindex a SQL database?

There's a general consensus that you should reorganize ("defragment") your indices as soon as index fragmentation reaches more than 5 (sometimes 10%), and you should rebuild them completely when it goes beyond 30% (at least that's the numbers I've heard advocated in a lot of places).

When should you use indexing?

The purpose of indexes is to enhance a database's performance, there are multiple scenarios where indexes should not be used.1Indexes should not be used on tables containing few records.2Tables that have frequent, large batch updates or insert operations.Indexes When to Use and When to Avoid In SQL. | Javarevisited

Why do we need to rebuild index in SQL Server?

Rebuilding an index drops and re-creates the index. This removes fragmentation, reclaims disk space by compacting the pages based on the specified or existing fill factor setting, and reorders the index rows in contiguous pages.

What does reindex do in SQL?

DBCC DBREINDEX rebuilds an index for a table or all indexes defined for a table. By allowing an index to be rebuilt dynamically, indexes enforcing either PRIMARY KEY or UNIQUE constraints can be rebuilt without having to drop and re-create those constraints.