DSN_PTASK_TABLE

The parallel tasks table, DSN_PTASK_TABLE, contains information about all of the parallel tasks in a query.

Begin program-specific programming interface information.

Recommendation: 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.

Qualifiers

Your subsystem or data sharing group can contain multiple instances of these 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. You can call the ADMIN_EXPLAIN_MAINT stored procedure to create EXPLAIN tables, upgrade them to the format for the current Db2 release, or complete other maintenance tasks. See ADMIN_EXPLAIN_MAINT stored procedure for information about using the action input parameter to request each of these tasks.

Column descriptions

The following table describes the columns of DSN_PTASK_TABLE.

Table 1. DSN_PTASK_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. When the SQL statement is embedded in a compiled SQL function, native SQL procedure, or advanced trigger, 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, native SQL procedure, or advanced trigger.
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.
PGDNO	SMALLINT NOT NULL	The parallel group identifier within the current query block. This value corresponds to the value of the GROUPID column in DSN_PGROUP_TABLE table rows.
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. When the SQL statement is embedded in a compiled SQL function, native SQL procedure, or advanced trigger, 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. When the SQL statement is embedded in an advanced trigger, this column contains the name of the trigger.
LPTNO	SMALLINT NOT NULL	The parallel task number.
KEYCOLID	SMALLINT	The key column ID (KEY range only).
DPSI	CHAR(1) NOT NULL	Indicates if a data partition secondary index (DPSI) is used.
LPTLOKEY	VARCHAR(40) FOR BIT DATA	The low key value for this key column for this parallel task (KEY range only).
LPTHIKEY	VARCHAR(40) FOR BIT DATA	The high key value for this key column for this parallel task (KEY range only).
LPTLOPAG	CHAR(4) FOR BIT DATA	The low page information if partitioned by page range.
LPTLHIPAG	CHAR(4) FOR BIT DATA	The high page information if partitioned by page range.
LPTLOPG¹	CHAR(4) FOR BIT DATA	The lower bound page number for this parallel task (Page range or DPSI enabled only).
LPTHIPG¹	CHAR(4) FOR BIT DATA	The upper bound page number for this parallel task (Page range or DPSI enabled only).
LPTLOPT¹	SMALLINT	The lower bound partition number for this parallel task (Page range or DPSI enabled only).
LPTHIPT¹	SMALLINT	The upper bound partition number for this parallel task (Page range or DPSI enabled only).
KEYCOLDT	SMALLINT	The data type for this key column (KEY range only).
KEYCOLPREC	SMALLINT	The precision/length for this key column (KEY range only).
KEYCOLSCAL	SMALLINT	The scale for this key column (KEY range with Decimal datatype 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.
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.
SECTNOI	INTEGER NOT NULL WITH DEFAULT WITH DEFAULT	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.
COLLID	VARCHAR(128) NOT NULL WITH DEFAULT	The collection ID: '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, native SQL procedure, or advanced trigger, this column indicates the schema name of the compiled SQL function, native SQL procedure, or advanced trigger.
VERSION	VARCHAR(122) NOT NULL WITH DEFAULT	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. If the value is not blank, the value is the same as the VERSION value for the package that was used to create this EXPLAIN table row. The value is blank for a statement in: A package for a basic trigger (TYPE='T') A package for an application that was precompiled without SQL processing option VERSION A package that was precompiled with an empty string for the VERSION value (TYPE=blank) When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the version identifier of the function or procedure. When the SQL statement is embedded in an advanced trigger body, this column is not used and will be blank.
EXPANSION_REASON	CHAR(2) NOT NULL WITH DEFAULT	This column applies only to statements that reference archive tables or temporal tables. For other statements, this column is blank. Indicates the effect of the CURRENT TEMPORAL BUSINESS_TIME special register, the CURRENT TEMPORAL SYSTEM_TIME special register, and the SYSIBMADM.GET_ARCHIVE built-in global variable. These items are controlled by the BUSTIMESENSITIVE, SYSTIMESENSITIVE, and ARCHIVESENSITIVE bind options. Db2 implicitly adds certain syntax to the query if one of the following conditions are true: The SYSIBMADM.GET_ARCHIVE global variable is set to Y and the ARCHIVESENSITIVE bind option is set to YES The CURRENT TEMPORAL BUSINESS_TIME special register is not null and the BUSTIMESENSITIVE bind option is set to YES The CURRENT TEMPORAL SYSTEM_TIME special register is not null and the SYSTIMESENSITIVE bind option is set to YES This column can have one of the following values: 'A' The query contains implicit query transformation as a result of the SYSIBMADM.GET_ARCHIVE built-in global variable. 'B' The query contains implicit query transformation as a result of the CURRENT TEMPORAL BUSINESS_TIME special register. 'S' The query contains implicit query transformation as a result of the CURRENT TEMPORAL SYSTEM_TIME special register. 'SB' The query contains implicit query transformation as a result of the CURRENT TEMPORAL SYSTEM_TIME special register and the CURRENT TEMPORAL BUSINESS_TIME special register. blank The query does not contain implicit query transformation.
PER_STMT_ID	BIGINT NOT NULL	The persistent statement identifier for SQL statements in Db2 catalog tables. For example, this column corresponds to the following catalog table columns that identify SQL statements: STMT_ID in SYSIBM.SYSPACKSTMT, for SQL statements in packages. SDQ_STMT_ID in SYSIBM.SYSDYNQUERY, for stabilized dynamic SQL statements.
AP_PLANID	CHAR(16) FOR BIT DATA	A unique identifier for BIND or PREPARE optimizations for an SQL statement, in the form of an extended timestamp value.

Notes:

The name of these columns originally contained the # symbol as the last character in the names. However, the names that contain these characters are obsolete and are no longer supported.

End program-specific programming interface information.