DB2 graphic QMF Version 8

Sample analysis help panel

The QMF Query Information Help panel (RAAQMFQB) is described in this section. All of the raw access path data available from Query Analyzer is shown on this panel. This panel is accessed from the QMF Query Information help facility.

Table 95. QMF Query Information Help
DB2P - QMF Query Information Help - Access Path Details ------------- 8.1.0
Command ===>
Press ENTER for a description of these values.
 
Number of Query Blocks..................................... :
Number of Tables Referenced................................ :
Access Types............................................... :
Number of Index Only Scans/Matching Index Scans............ :
Join Methods............................................... :
Join Types................................................. :
Prefetch Types............................................. :
Number of Page Range Screens............................... :
DB2 Sorting................................................ :
Parallelism Modes/Highest Access Degree.................... :
Column Functions Evaluation Types.......................... :
 
 
 
 
 
 
 
 
 

The fields on the panel are:

Number of Query Blocks
The highest number found in the QBLOCKNO column of the plan table. It represents the number of queries in the SQL statement.
Number of Tables Referenced
The total number of table names occurrences found in the plan table. An occurrence of a table name is a non-blank value in the TNAME column of the plan table. This column can contain a name of a table, view, table expression or temporary table. Duplicates will be counted as separate references. For a list of table names found in the plan table, see Table Creator/Name on page ***.
Access Types
The different methods of accessing the tables found in the plan table. The values listed here are from the ACCESSTYPE column of the plan table. Duplicates are not shown.
Number of Index Only Scans/Matching Index Scans
A total number of occurrences of the value Y (Yes) in the INDEXONLY column of the plan table. This represents the number of steps within the plan that can be satisfied with an index read only (no data access necessary). If the Number of Query Blocks, described above, equals this number, then all queries in the statement are satisfied using an index only. The Number of Matching Index Scans represent the number of occurrences of the MATCHCOLS column where the value is greater than zero. It is not the actual number of columns matching on the index, but rather the number of times the index keys are used in an index scan.
Join Methods
A list of the different types of join methods found in the plan table. The values listed come from the METHOD column of the plan table. Duplicates are not included.
Join Types
A list of the different types of joins found in the plan table. The values listed come from the JOIN_TYPE column of the plan table. Only outer joins are listed (inner joins are blank) and a Left Outer join (L) is equivalent to a Right Outer join. Duplicates are NOT included.
Prefetch Types
A list of the different types of prefetch, if any, found in the plan table. If prefetching is possible, it will be a sequential (S) prefetch or a list (L) prefetch as listed in the PREFETCH column of the plan table. Duplicates are NOT included.
Number of Page Range Screens
The total number of occurrences of tables that qualify for page range screening. For every value equal to Y (Yes) in the column PAGE_RANGE of the plan table, this number is incremented by one. The total Number of Page Range Screens found and the Number of Tables Referenced, described above, can be used to determine percentages of page range screening per table access within the query.
DB2 Sorting
This value indicates whether any DB2 sorting was found in the plan table. A value of Y (Yes) for any of the SORTN_ or SORTC_ columns would trigger a Y indicator for this field.
Parallelism Modes/Highest Access Degree
Parallelism modes list the types of parallelism available at bind time. If a value of I or C (I/O or CPU parallelism) is found for any step in the plan in column PARALLELISM_MODE, then the highest access degree field can be non-zero. The highest access degree represents the greatest number of parallel tasks available for any step in the plan table activated by the query. This is the highest value found in the ACCESS_DEGREE column of the plan table and does not include the JOIN_DEGREE value.
Column Functions Evaluation Types
A list of the different types of column function evaluations, if any, found in the plan table. The values can be an S (function evaluated while performing a sort to satisfy a GROUP BY clause) or R (column function evaluated while data is being read). If NONE is listed, then function may be evaluated after data retrieval and any sorts, or if ACCESSTYPE = I1 and MIN or MAX function is present, at index access time. Duplicates are not included.


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timestamp Last updated: March, 2004