DSN_DETCOST_TABLE

The detailed cost table, DSN_DETCOST_TABLE, contains information about detailed cost estimation of the mini-plans in a query.

Begin program-specific programming interface information.
Recommendation: Start of changeDo not manually insert data into system-maintained EXPLAIN tables, and use care when deleting obsolete EXPLAIN table data. The data is intended to be manipulated only by the DB2® EXPLAIN function and optimization tools. Certain optimization tools depend on instances of the various EXPLAIN tables. Be careful not to delete data from or drop instances EXPLAIN tables that are created for these tools.End of change

Qualifiers

Your subsystem or data sharing group can contain more than one of these tables:
'SYSIBM'
Start of changeOne instance of this table can be created with the SYSIBM qualifier. DB2 and SQL optimization tools might use the table and the data that it contains. The table is created when you run job DSNTIJSG when you install or migrate DB2.End of change
'user-ID'
You can create additional instances of EXPLAIN tables that are qualified by user ID. These tables are populated with statement cost information when you issue the EXPLAIN statement or bind. They are also populated when you specify EXPLAIN(YES) or EXPLAIN(ONLY) in a BIND or REBIND command. SQL optimization tools might also create EXPLAIN tables that are qualified by a user ID. You can find the SQL statement for creating an instance of these tables in member DSNTESC of the SDSNSAMP library.

Sample CREATE TABLE statement

You can find a sample CREATE TABLE statement for each EXPLAIN table in member DSNTESC of the prefix.SDSNSAMP library.

Column descriptions

The following table describes the columns of DSN_DETCOST_TABLE.

Table 1. DSN_DETCOST_TABLE description
Column name Data type Description
QUERYNO INTEGER NOT NULL A number that identifies the statement that is being explained. The origin of the value depends on the context of the row:
For rows produced by EXPLAIN statements
The number specified in the QUERYNO clause, which is an optional part of the SELECT, INSERT, UPDATE, MERGE, and DELETE statement syntax.
For rows not produced by EXPLAIN statements
DB2 assigns a number that is based on the line number of the SQL statement in the source program.

When the values of QUERYNO are based on the statement number in the source program, values that exceed 32767 are reported as 0. However, in certain rare cases, the value is not guaranteed to be unique.

Start of changeWhen the SQL statement is embedded in a compiled SQL function or native SQL procedure, if the QUERYNO clause is specified, its value is used by DB2. Otherwise DB2 assigns a number based on the line number of the SQL statement in the compiled SQL function or native SQL procedure.End of change
QBLOCKNO SMALLINT NOT NULL A number that identifies each query block within a query. The value of the numbers are not in any particular order, nor are they necessarily consecutive.
APPLNAME VARCHAR(24) NOT NULL The name of the application plan for the row. Applies only to embedded EXPLAIN statements that are executed from a plan or to statements that are explained when binding a plan. A blank indicates that the column is not applicable.

Start of changeWhen the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column is not used, and is blank.End of change
PROGNAME VARCHAR(128) NOT NULL The name of the program or package containing the statement being explained. Applies only to embedded EXPLAIN statements and to statements explained as the result of binding a plan or package. A blank indicates that the column is not applicable.

Start of changeWhen the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the specific name of the compiled SQL function or native SQL procedure.End of change
PLANNO SMALLINT NOT NULL The plan number, a number used to identify each mini-plan with a query block.
OPENIO FLOAT(4) NOT NULL The Do-at-open IO cost for non-correlated subquery.
OPENCPU FLOAT(4) NOT NULL The Do-at-open CPU cost for non-correlated subquery.
OPENCOST FLOAT(4) NOT NULL The Do-at-open total cost for non-correlated subquery.
DMIO FLOAT(4) NOT NULL IBM® internal use only.
DMCPU FLOAT(4) NOT NULL IBM internal use only.
DMTOT FLOAT(4) NOT NULL IBM internal use only.
SUBQIO FLOAT(4) NOT NULL IBM internal use only.
SUBQCOST FLOAT(4) NOT NULL IBM internal use only.
BASEIO FLOAT(4) NOT NULL IBM internal use only.
BASECPU FLOAT(4) NOT NULL IBM internal use only.
BASETOT FLOAT(4) NOT NULL IBM internal use only.
ONECOMPROWS FLOAT(4) NOT NULL The number of rows qualified after applying local predicates.
IMLEAF FLOAT(4) NOT NULL The number of index leaf pages scanned by Data Manager.
IMIO FLOAT(4) NOT NULL IBM internal use only.
IMPREFH CHAR(2) NOT NULL IBM internal use only.
IMMPRED INTEGER NOT NULL IBM internal use only.
IMFF FLOAT(4) NOT NULL The filter factor of matching predicates only.
IMSRPRED INTEGER NOT NULL IBM internal use only.
IMFFADJ FLOAT(4) NOT NULL The filter factor of matching and screening predicates.
IMSCANCST FLOAT(4) NOT NULL IBM internal use only.
IMROWCST FLOAT(4) NOT NULL IBM internal use only.
IMPAGECST FLOAT(4) NOT NULL IBM internal use only.
IMRIDSORT FLOAT(4) NOT NULL IBM internal use only.
IMMERGCST FLOAT(4) NOT NULL IBM internal use only.
IMCPU FLOAT(4) NOT NULL IBM internal use only.
IMTOT FLOAT(4) NOT NULL IBM internal use only.
IMSEQNO SMALLINT NOT NULL IBM internal use only.
DMPEREFH FLOAT(4) NOT NULL IBM internal use only.
DMCLUDIO FLOAT(4) NOT NULL IBM internal use only.
DMPREDS INTEGER NOT NULL IBM internal use only.
DMSROWS FLOAT(4) NOT NULL IBM internal use only.
DMSCANCST FLOAT(4) NOT NULL IBM internal use only.
DMCOLS FLOAT(4) NOT NULL The number of data manager columns.
DMROWS FLOAT(4) NOT NULL The number of data manager rows returned (after all stage 1 predicates are applied).
RDSROWCST FLOAT(4) NOT NULL IBM internal use only.
DMPAGECST FLOAT(4) NOT NULL IBM internal use only.
DMDATAIO FLOAT(4) NOT NULL IBM internal use only.
DMDATAIO FLOAT(4) NOT NULL IBM internal use only.
DMDATACPU FLOAT(4) NOT NULL IBM internal use only.
DMDATACPU FLOAT(4) NOT NULL IBM internal use only.
RDSROW FLOAT(4) NOT NULL The number of RDS rows returned (after all stage 1 and stage 2 predicates are applied).
SNCOLS SMALLINT NOT NULL The number of columns as sort input for new table.
SNROWS FLOAT(4) NOT NULL The number of rows as sort input for new table.
SNRECSZ INTEGER NOT NULL The record size for new table.
SNPAGES FLOAT(4) NOT NULL The page size for new table.
SNRUNS FLOAT(4) NOT NULL The number of runs generated for sort of new table.
SNMERGES FLOAT(4) NOT NULL The number of merges needed during sort.
SNIOCOST FLOAT(4) NOT NULL IBM internal use only.
SNCPUCOST FLOAT(4) NOT NULL IBM internal use only.
SNCOST FLOAT(4) NOT NULL IBM internal use only.
SNCSCANIO FLOAT(4) NOT NULL IBM internal use only.
SNSCANCPU FLOAT(4) NOT NULL IBM internal use only.
SNCCOLS FLOAT(4) NOT NULL The number of columns as sort input for Composite table.
SCROWS FLOAT(4) NOT NULL The number of rows as sort input for Composite Table.
SCRECSZ FLOAT(4) NOT NULL The record size for Composite table.
SCPAGES FLOAT(4) NOT NULL The page size for Composite table.
SCRUNS FLOAT(4) NOT NULL The number of runs generated during sort of composite.
SCMERGES FLOAT(4) NOT NULL The number of merges needed during sort of composite.
SCIOCOST FLOAT(4) NOT NULL IBM internal use only.
SCCPUCOST FLOAT(4) NOT NULL IBM internal use only.
SCCOST FLOAT(4) NOT NULL IBM internal use only.
SCSCANIO FLOAT(4) NOT NULL IBM internal use only.
SCSCANCPU FLOAT(4) NOT NULL IBM internal use only.
SCSCANCOST FLOAT(4) NOT NULL IBM internal use only.
COMPCARD FLOAT(4) NOT NULL The total composite cardinality.
COMPIOCOST FLOAT(4) NOT NULL IBM internal use only.
COMPCPUCOST FLOAT(4) NOT NULL IBM internal use only.
COMPCOST FLOAT(4) NOT NULL The total cost.
JOINCOLS SMALLINT NOT NULL IBM internal use only.
EXPLAIN_TIME TIMESTAMP NOT NULL The time when the EXPLAIN information was captured:
All cached statements
When the statement entered the cache, in the form of a full-precision timestamp value.
Non-cached static statements
When the statement was bound, in the form of a full precision timestamp value.
Non-cached dynamic statements
When EXPLAIN was executed, in the form of a value equivalent to a CHAR(16) representation of the time appended by 4 zeros.
COSTBLK INTEGER NOT NULL IBM internal use only.
COSTSTOR INTEGER NOT NULL IBM internal use only.
MPBLK INTEGER NOT NULL IBM internal use only.
MPSTOR INTEGER NOT NULL IBM internal use only.
COMPOSITES INTEGER NOT NULL IBM internal use only.
CLIPPED INTEGER NOT NULL IBM internal use only.
TABREF VARCHAR(64) NOT NULL FOR BIT DATA IBM internal use only.
MAX_COMPOSITES INTEGER NOT NULL IBM internal use only.
MAX_STOR INTEGER NOT NULL IBM internal use only.
MAX_CPU INTEGER NOT NULL IBM internal use only.
MAX_ELAP INTEGER NOT NULL IBM internal use only.
TBL_JOINED_THRESH INTEGER NOT NULL IBM internal use only.
STOR_USED INTEGER NOT NULL IBM internal use only.
CPU_USED INTEGER NOT NULL IBM internal use only.
ELAPSED INTEGER NOT NULL IBM internal use only.
MIN_CARD_KEEP FLOAT(4) NOT NULL IBM internal use only.
MAX_CARD_KEEP FLOAT(4) NOT NULL IBM internal use only.
MIN_COST_KEEP FLOAT(4) NOT NULL IBM internal use only.
MAX_COST_KEEP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_KEEP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_CARD_KEEP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_COST_KEEP FLOAT(4) NOT NULL IBM internal use only.
MIN_CARD_CLIP FLOAT(4) NOT NULL IBM internal use only.
MAX_CARD_CLIP FLOAT(4) NOT NULL IBM internal use only.
MIN_COST_CLIP FLOAT(4) NOT NULL IBM internal use only.
MAX_COST_CLIP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_CLIP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_CARD_CLIP FLOAT(4) NOT NULL IBM internal use only.
MIN_VALUE_COST_CLIP FLOAT(4) NOT NULL IBM internal use only.
MAX_VALUE_CLIP FLOAT(4) NOT NULL IBM internal use only.
MAX_VALUE_CARD_CLIP FLOAT(4) NOT NULL IBM internal use only.
MAX_VALUE_COST_CLIP FLOAT(4) NOT NULL IBM internal use only.
GROUP_MEMBER VARCHAR(24) NOT NULL The member name of the DB2 that executed EXPLAIN. The column is blank if the DB2 subsystem was not in a data sharing environment when EXPLAIN was executed.
PSEQIOCOST FLOAT(4) NOT NULL IBM internal use only.
PSEQIOCOST FLOAT(4) NOT NULL IBM internal use only.
PSEQCPUCOST FLOAT(4) NOT NULL IBM internal use only.
PSEQCOST FLOAT(4) NOT NULL IBM internal use only.
PADJIOCOST FLOAT(4) NOT NULL IBM internal use only.
PADJCPUCOST FLOAT(4) NOT NULL IBM internal use only.
PADJCOST FLOAT(4) NOT NULL IBM internal use only.
Start of changeUNCERTAINTYEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeDescribes the uncertainty factor of inner table index access. It is aggregated from uncertainty of inner table probing predicates. A larger value indicates a higher uncertainty. 0 indicates no uncertainty or uncertainty not considered.End of change
Start of changeUNCERTAINTY_1TEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeDescribes the uncertainty factor of ONECOMPROWS column of the table. It is aggregated from all local predicates on the table. A larger value indicates a higher uncertainty. 0 indicates no uncertainty or uncertainty not considered.End of change
Start of changeSECTNOIEnd of change Start of changeINTEGER NOT NULL WITH DEFAULTEnd of change Start of changeThe section number of the statement. The value is taken from the same column in SYSPACKSTMT or SYSSTMT tables and can be used to join tables to reconstruct the access path for the statement. This column is applicable only for static statements. The default value of -1 indicates EXPLAIN information that was captured in DB2 9 or earlier.End of change
Start of changeCOLLIDEnd of change Start of changeVARCHAR(128) NOT NULLEnd of change Start of changeThe collection ID:
'DSNDYNAMICSQLCACHE'
The row originates from the dynamic statement cache
Start of change'DSNEXPLAINMODEYES'End of change
Start of changeThe row originates from an application that specifies YES for the value of the CURRENT EXPLAIN MODE special register.End of change
Start of change'DSNEXPLAINMODEEXPLAIN'End of change
Start of changeThe row originates from an application that specifies EXPLAIN for the value of the CURRENT EXPLAIN MODE special register.End of change

Start of changeWhen the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the schema name of the compiled SQL function or native SQL procedure.End of change

End of change
Start of changeVERSIONEnd of change Start of changeVARCHAR(128) NOT NULL WITH DEFAULTEnd of change Start of changeThe version identifier for the package. Applies only to an embedded EXPLAIN statement executed from a package or to a statement that is explained when binding a package. A blank indicates that the column is not applicable.

Start of changeWhen the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the schema name of the compiled SQL function or native SQL procedure.End of change

End of change
Start of changeIMNPEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeDMNPEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeIMJCEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeIMFCEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeIMJBCEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeIMJFCEnd of change Start of changeFLOAT(4) NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
Start of changeCREDEnd of change Start of changeINTEGER NOT NULL WITH DEFAULTEnd of change Start of changeIBM internal use only.End of change
End program-specific programming interface information.