SQL/MX 2.x Query Guide (G06.24+, H06.03+)

Reviewing Query Execution Plans

HP NonStop SQL/MX Query Guide—523728-003

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Verifying DAM Access

You can verify if operators are executing in DAM by reviewing the EXPLAIN output for

the plan. If the plan shows the PARTITION_ACCESS operator, DAM access is being

used. Operators appearing below the PARTITION_ACCESS operator are executing in

DAM.

Using the Visual Query Planner

Visual Query Planner is a Microsoft Windows NT GUI application that enables you to

extract and display query execution plans generated by the SQL/MX optimizer for DML

statements. Visual Query Planner uses the EXPLAIN function internally to extract the

information about the query plan.

You can save plans that you generate for further analysis. Saved plans can be sent to

anyone who can look at them without having to access the actual database. You can

also provide plans to the Global Customer Support Center (GCSC) in case of

problems. Visual Query Planner also provides the ability to force the optimizer to

present the plan that you design. For further information, see Section 5, Forcing

Execution Plans.

Visual Query Planner Requirements

In addition to SQL/MX, Visual Query Planner requires that you have data sources

defined for ODBC. You must have a PC or workstation with Windows NT 4.0 (or later)

to use Visual Query Planner. For information about installing Visual Query Planner,

see the SQL/MX Installation and Management Guide. For information about defining

ODBC data sources with the Microsoft ODBC Data Source Administrator, see the

ODBC Driver for Windows Manual.

Figure 4-1. Left Linear and Zig-Zag Trees

Note. To avoid unexpected results, turn off query caching at the start of your VQP session.

Left Linear Tree

Zig-Zag Tree

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