View Explain

To show the Explain Plan of the query, press Preview and choose Explain or Preview and Explain. If the query statement is correct, the Explain tab opens with the columns in the PLAN_TABLE.

The Explain tab displays the data in the Oracle PLAN_TABLE as a grid:

Column
Description
STATEMENT_ID Value of the optional STATEMENT_ID parameter specified in the EXPLAIN PLAN statement.
PLAN_ID Unique identifier of a plan in the database.
TIMESTAMP Date and time when the EXPLAIN PLAN statement was generated.
REMARKS Any comment (of up to 80 bytes) you want to associate with each step of the explained plan. This column is used to indicate whether an outline or SQL Profile was used for the query.
OPERATION Name of the internal operation performed in this step.
OPTIONS A variation on the operation described in the OPERATION column.
OBJECT_NODE

Name of the database link used to reference the object (a table name or view name). For local queries using parallel execution, this column describes the order in which output from operations is consumed.

OBJECT_OWNER

Name of the user who owns the schema containing the table or index.

OBJECT_NAME

Name of the table or index.

OBJECT_ALIAS

Unique alias of a table or view in a SQL statement. For indexes, it is the object alias of the underlying table.

OBJECT_INSTANCE

Number corresponding to the ordinal position of the object as it appears in the original statement. The numbering proceeds from left to right, outer to inner with respect to the original statement text. View expansion results in unpredictable numbers.

OBJECT_TYPE

Modifier that provides descriptive information about the object; for example, NON-UNIQUE for indexes.

OPTIMIZER

Current mode of the optimizer.

SEARCH_COLUMNS

Not currently used.

ID

A number assigned to each step in the execution plan.

PARENT_ID

The ID of the next execution step that operates on the output of the ID step.

DEPTH

Depth of the operation in the row source tree that the plan represents. The value can be used for indenting the rows in a plan table report.

POSITION

For the first row of output, this indicates the optimizer's estimated cost of executing the statement. For the other rows, it indicates the position relative to the other children of the same parent.

COST

Cost of the operation as estimated by the optimizer's query approach.

CARDINALITY

Estimate by the query optimization approach of the number of rows accessed by the operation.

BYTES

Estimate by the query optimization approach of the number of bytes accessed by the operation.

OTHER_TAG

Describes the contents of the OTHER column.

PARTITION_START

Start partition of a range of accessed partitions.

PARTITION_STOP

Stop partition of a range of accessed partitions.

PARTITION_ID

Step that has computed the pair of values of the PARTITION_START and PARTITION_STOP columns.

OTHER

Other information that is specific to the execution step that a user might find useful. See the OTHER_TAG column.

DISTRIBUTION

Method used to distribute rows from producer query servers to consumer query servers.

CPU_COST

CPU cost of the operation as estimated by the query optimizer's approach. The value of this column is proportional to the number of machine cycles required for the operation.

IO_COST

I/O cost of the operation as estimated by the query optimizer's approach. The value of this column is proportional to the number of data blocks read by the operation.

TEMP_SPACE

Temporary space, in bytes, used by the operation as estimated by the query optimizer's approach.

ACCESS_PREDICATES

Predicates used to locate rows in an access structure.

FILTER_PREDICATES

Predicates used to filter rows before producing them.

PROJECTION

Expressions produced by the operation.

TIME

Elapsed time in seconds of the operation as estimated by query optimization.

QBLOCK_NAME

Name of the query block, either system-generated or defined by the user with the QB_NAME hint.