Sample analysis output panel
The QMF Query Information panel (RAAQMFQA) is described
in this section. All of the data available from Query Analyzer are
shown on this panel.
Table 94. Query Information
DB2P - QMF Query Information ------------------------------------------ 8.1.0
Command ===>
Is access through an index?................................ :
Is access through more than one index?..................... :
How many indexes use matching columns?..................... :
Is the query satisfied using only the index?............... :
Was a scan limited to certain partitions?.................. :
Is prefetching performed?.................................. :
Is data accessed/processed in parallel?.................... :
Are sorts performed?....................................... :
Are joins present in the query?............................ :
When are column functions evaluated?....................... :
Cost category-Service Units (in 100s) to run query......... :
Historical Data For This Query
Minimum rows...... : Minimum CPU time......... :
Maximum rows...... : Maximum CPU time......... :
Average rows...... : Average CPU time......... :
Enter Y or press PF3 to cancel this query ===>
Enter maximum number of rows to fetch.... ===> (0=bypass) |
If you press PF1, a description of these
fields and the raw access path data are available for display.
The fields on the panel are:
- Is access through an index?
- If an access type of I, I1, N, or MX is found in the EXPLAIN
output, then this field is set to YES. This indicates that there
is at least one instance of index access, although other access
types may also be present.
- Is access through more than one index?
- If an access type of M, MX, MI, or MU is found in the EXPLAIN
output, then this field is set to YES. This indicates at least one
instance of a multiple index access.
- How many indexes use matching columns?
- If index access is found in the plan and MATCHCOLS > 0,
then this number is incremented by 1. This is not the number of
matching columns per index nor is it the sum of the number of matching
columns, but rather it is the number of index accesses in which
columns in a WHERE condition matched columns of the index. This
is equal to the Matching Index scans field on the Help panel.
- Is the query satisfied using only the index?
- If any query in the plan has an INDEXONLY
column = YES, then this field will be set to YES.
- Was a scan limited to certain partitions?
- If PAGE_RANGE = Y for any row in the plan table, then this
field will be set to YES.
- Is prefetching performed?
- If PREFETCH is L or S for any row of the plan table, then
this field will be set to YES.
- Is data accessed/processed in parallel?
- If PARALLELISM_MODE is I or C for any row in the plan table,
then this field is set to YES.
- Are sorts performed?
- If any of the SORTN_ or SORTC_ columns of the plan table are
Y, then this field is set to YES. Also, if Join Method = 3, this
also indicates a sort was performed.
- Are joins present in the query?
- If METHOD = 1,2, or 4 for any row in the plan table, then
this field is set to YES.
- When are column functions evaluated?
- This value can be S and/or R according to COLUMN_FN_EVAL in the plan table. SQL Parsing
is not performed to determine specific function type.
- Cost Category and Service Units to run query
- This is the estimated processor cost for this SQL statement.
This value is comprised of the Cost Category and the Service Units.
Both these values come from the DSN STATEMNT TABLE and are present
only if the release level of DB2 is 6.1 or higher.
- Cost Category
- Indicates which values DB2 used to make the estimate.
- A indicates DB2 had enough information
to make the estimate without using defaults.
- B indicates DB2 had some condition that
forced it to use defaults and, as a result, estimates may not be
as accurate.
- Service Units
- Estimated processor cost for this SQL statement in units of
100. For example, a displayed value of 21 means approximately 2100 service
units (the value is truncated).
- Historical data for query
- This area of the panel shows the actual historical values
saved from previous runs of the named object. The object name and
associated statistics will be displayed only if they are available.
Because object history is tracked by QMF object name, queries run
with no associated object name will not be able to access historical
statistics. Given the case where the object has been tracked, the
information shown is the minimum, maximum, and average counts for
both rows fetched and CPU utilization (the CPU time shown is in
HH:MM:SS:HS format).
- Query will be canceled by Query Analyzer
- If the exit routine has determined that the query should be
canceled, then this message will appear at the bottom of the panel.
- Enter Y or press PF3 to cancel this query
- If you specify Y and press Enter or press PF3,
this query will not run and you will return to the previous QMF
panel. If you leave this field blank and press Enter,
this query will run.
- Enter maximum number of rows to fetch (0=bypass)
- This value determines the number of rows that QMF will fetch
before the query is canceled. A value of 0 (zero) directs Query
Analyzer to bypass this row limit checking. The value entered here
will not override the row limit enforced by Governor.
