DSN_COLDIST_TABLE

The column distribution table contains non-uniform column group statistics that are obtained dynamically by DB2® from non-index leaf pages.

Begin program-specific programming interface information.

Recommendation: Start of change

Do 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': One 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.
'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 shows the descriptions of the columns in the DSN_COLDIST_TABLE table.

Table 1. Descriptions of columns in DSN_COLDIST_TABLE
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. When 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.
APPLNAME	VARCHAR(128) 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. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column is not used, and is blank.
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. When 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.
COLLID	VARCHAR(128) NOT NULL	The collection ID: 'DSNDYNAMICSQLCACHE' The row originates from the dynamic statement cache 'DSNEXPLAINMODEYES' The row originates from an application that specifies YES for the value of the CURRENT EXPLAIN MODE special register. 'DSNEXPLAINMODEEXPLAIN' The row originates from an application that specifies EXPLAIN for the value of the CURRENT EXPLAIN MODE special register. When 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.
GROUP_MEMBER	VARCHAR(128) 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.
SECTNOI	INTEGER NOT NULL	The 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.
VERSION	VARCHAR(122) NOT NULL	The 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. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the version identifier of the compiled SQL function or native SQL procedure.
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.
SCHEMA	VARCHAR(128) NOT NULL	The schema of the table that contains the column.
TBNAME	VARCHAR(128) NOT NULL	The name of the table that contains the column.
NAME	VARCHAR(128) NOT NULL	Name of the column. If the value of NUMCOLUMNS is greater than 1, this name identifies the first column name of the set of columns associated with the statistics.
COLVALUE	VARCHAR(2000) NOT NULL FOR BIT DATA	Contains the data of a frequently occurring value in the column. Statistics are not collected for an index on a ROWID column. If the value has a non-character data type, the data might not be printable. This column might contain values that depend on the value of the type column: TYPE='T' One of the following values: 'E3C2C1C3C1D9C4C6' for TBACARDF 'E3C2C1D5C1C3E3C6' for TBANPAGF 'E3C2C1D5D7C1C7C6' for TBANACTF TYPE='L' 'C3C1E3C6D3C4C3C6' for CATFLDCF TYPE='P' One of the following values: 'D7C3C1D7D5D9E6C6' for PCAPNRWF 'D7C3C1D7D5D7C7C6' for PCAPNPGF
TYPE	CHAR(1) NOT NULL	The type of statistics: C Cardinality F Frequent value H Histogram T Real-time table cardinality L Real-time column cardinality (unique index only) P real-time partition cardinality
CARDF	FLOAT NOT NULL	For TYPE='C', the number of distinct values for the column group. For TYPE='H', the number of distinct values for the column group in a quantile indicated by the value of the QUANTILENO column. For TYPE='T', a value related to real-time statistics table values that are determined by the COLVALUE column. For TYPE= 'L', a value related to a real-time statistics column value that is determined by the COLVALUE column. The QUANTILENO column contains the column number. The NAME column contains the column name. For TYPE='P' a value related to real-time statistics partition value that is determined by the COLVALUE column. The QUANTILENO column contains the partition number.
COLGROUPCOLNO	VARCHAR(254) NOT NULL FOR BIT DATA	The identity of the set of columns associated with the statistics. If the statistics are only associated with a single column, the field contains a zero length. Otherwise, the field is an array of SMALLINT column numbers with a dimension equal to the value in the NUMCOLUMNS column. This is an updatable column.
NUMCOLUMNS	SMALLINT NOT NULL	Identifies the number of columns associated with the statistics.
FREQUENCYF	FLOAT NOT NULL	The percentage of rows in the table with the value that is specified in the COLVALUE column when the number is multiplied by 100. For example, a value of '1' indicates 100%. A value of '.153' indicates 15.3%.
QUANTILENO	SMALLINT NOT NULL	The ordinary sequence number of a quantile in the whole consecutive value range, from low to high. This column is not updatable. For TYPE= 'L', this column contains the column number. For TYPE='P', the column contains the partition number.
LOWVALUE	VARCHAR(2000) NOT NULL FOR BIT DATA	For TYPE='H', this is the lower bound for the quantile indicated by the value of the QUANTILENO column. Not used if the value of the TYPE column is not 'H'. This column is not updatable.
HIGHVALUE	VARCHAR(2000) NOT NULL FOR BIT DATA	For TYPE='H', this is the higher bound for the quantile indicated by the value of the QUANTILENO column. This column is not used if the value of the TYPE column is not 'H'. This column is not updatable.

End program-specific programming interface information.