The Access Methods object in SQL Server provides counters to monitor how the logical data within the database is accessed. Physical access to the database pages on disk is monitored using the Buffer Manager counters. Monitoring the methods used to access data stored in the database can help you to determine whether query performance can be improved by adding or modifying indexes, adding or moving partitions, adding files or file groups, defragmenting indexes, or by rewriting queries. The Access Methods counters can also be used to monitor the amount of data, indexes, and free space within the database, thereby indicating data volume and fragmentation for each server instance. Excessive index fragmentation can impair performance.