Explain tab

The Explain tab displays a visual representation of the Db2 Explain plan.

You can view the Db2 statement in the following formats:

Explain diagram - displays each step as a node and indicates the step's cost, type, and message severity level
The node displays one of the following icons to indicate the highest severity of the message rules associated with that step (if a message rule exists):
- Severe
- Warning
- Informational
To focus on specific steps, you can zoom in and out.
Explain tree - you can expand or hide steps to focus on specific steps

Graphical Explain enables you to perform the following tasks:

Task	Description
View step details	Perform one of the following actions: In the Explain diagram, click the step node. In the Explain tree, click the node. In the Explain detail pane, select the Step Details tab to view the step information from the plan table.
View message rules	Perform one of the following actions: In the Explain diagram, click the step node. In the Explain tree, click the node. In the Explain detail pane, select the Message Rules tab to view the message rules (both those delivered by BMC and user-defined message rules).
Toggle between the Explain diagram and Explain tree formats	To display the Explain diagram, click Show graph view . To display the Explain tree, click Show tree view .
Zoom in and out	Move the Zoom slider or use the mouse wheel. To change which section of the Explain diagram is displayed, click and hold the mouse button while moving the mouse. To display the entire diagram on the page, click Fit on screen.
Enter full screen mode	Click Full screen .
Exit full screen mode	Click Close .
Expand or hide steps in the Explain tree	Click the expansion arrow next to the step node.

You can view the Db2 statement in the following formats:

Explain diagram - displays each step as a node and indicates the step's cost, type, and message severity level. The following icons indicate the step's type:
- Operator
- Query block
- Table
- Index
The node displays one of the following icons to indicate the highest severity of the message rules associated with that step (if a message rule exists):
- Severe
- Warning
- Informational
To focus on specific steps, you can move the nodes around the screen and zoom in and out.
Explain tree - you can expand or hide steps in order to focus on specific steps

Graphical Explain enables you to perform the following tasks:

Task	Description
View step details	Perform one of the following actions: In the Explain diagram, click the linked step name of a node. In the Explain tree, click the node. In the Explain Detail property box, select the Step Details tab to view the step information from the plan table.
View message rules	Perform one of the following actions: In the Explain diagram, click the linked step name of a node. In the Explain tree, click the node. In the Explain Detail property box, select the Message Rules tab to view the message rules (both those delivered by BMC and user-defined message rules).
Toggle between the Explain diagram and Explain tree formats	Click the Explain Display toggle .
Move the node	Click the step node and hold the mouse button while moving the mouse.
Zoom in and out	Move the Zoom slider, or repeatedly click Zoom in or Zoom out . To change which section of the Explain diagram is displayed, click and hold the mouse button while moving the mouse.
Move a node in the diagram to the top of the screen	To move a node in a diagram to the top of the screen, double-click the node. Tip Clicking Reset Diagram reverts to the initial state of the graph.
Revert the positioning of the Explain diagram to the initial positions	Click Reset Diagram .
Expand or hide steps in the Explain tree	Click the expansion arrow next to the step node.

Related topic

Performance perspective

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