The Scans event classes can be used to monitor when a table or index is being scanned during the execution of a query.
| Event class | Description |
|---|---|
| Scan: Started | Table or index scan has started. |
| Scan: Stopped | Table or index scan has stopped. |
These are the event-specific data columns for the Scans event category.
| Event class | Data column | Description |
|---|---|---|
| Scan: Started | Event Sub Class | Scan mode represented as a bitmap |
| Index ID | Index that is being scanned | |
| Object ID | Object that is being scanned | |
| Scan: Stopped | Event Sub Class | Scan mode represented as a bitmap |
| Index ID | Index that is being scanned | |
| Object ID | Object that is being scanned |
Using the Scan:Started and Scan:Stopped event classes, it is possible to monitor the type of scans being performed by a query on a specific object.
The scan modes for the Event Sub Class data column are:
| Value | Scan mode |
|---|---|
| 1 | Normal |
| 2 | First |
| 4 | Back |
| 8 | Unordered |
| 16 | No data |
| 32 | Reserved |
| 64 | Exlatch |
| 128 | Index supplied |
| 256 | Marker |
By monitoring the Index ID default data column, you can determine the identification number of the index being used by a specific query. The Index ID data column contains either: