CREATE SERVICE CLASS statement

The CREATE SERVICE CLASS statement defines a service class.

Invocation

This statement can be embedded in an application program or issued through the use of dynamic SQL statements. It is an executable statement that can be dynamically prepared only if DYNAMICRULES run behavior is in effect for the package (SQLSTATE 42509).

Authorization

The privileges held by the authorization ID of the statement must include WLMADM or DBADM authority.

Syntax

Read syntax diagramSkip visual syntax diagramCREATE SERVICE CLASSservice-class-name UNDERservice-superclass-name HARD CPU SHARES 1000HARDSOFTCPU SHARESinteger-constant CPU LIMITinteger-constantNONEDEGREE SCALEBACK DEFAULT1DEGREE SCALEBACKONOFFMAXIMUM DEGREE DEFAULT2MAXIMUM DEGREENONEdegreePREFETCH PRIORITY DEFAULTPREFETCH PRIORITYHIGHMEDIUMLOWOUTBOUND CORRELATOR NONEOUTBOUND CORRELATORstring-constantBUFFERPOOL PRIORITY DEFAULTBUFFERPOOL PRIORITYHIGHMEDIUMLOWCOLLECT AGGREGATE ACTIVITY DATA NONE3COLLECT AGGREGATE ACTIVITY DATABASEEXTENDEDCOLLECT AGGREGATE REQUEST DATA NONECOLLECT AGGREGATE REQUEST DATABASECOLLECT AGGREGATE UNIT OF WORK DATANONECOLLECT AGGREGATE UNIT OF WORK DATABASECOLLECT REQUEST METRICSNONE4COLLECT REQUEST METRICSBASEEXTENDED 5 histogram-template-clauseENABLEDISABLE
collect-activity-clause
Read syntax diagramSkip visual syntax diagram COLLECT ACTIVITY DATANONECOLLECT ACTIVITY DATAcollect-activity-data-clause
collect-activity-data-clause
Read syntax diagramSkip visual syntax diagramON COORDINATORMEMBERON ALLMEMBERSWITHOUT DETAILSWITH,DETAILS6SECTIONINCLUDE ACTUALS BASEAND VALUES
histogram-template-clause
Read syntax diagramSkip visual syntax diagram● ACTIVITY LIFETIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMACTIVITY LIFETIME HISTOGRAM TEMPLATEtemplate-name ● ACTIVITY QUEUETIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMACTIVITY QUEUETIME HISTOGRAM TEMPLATEtemplate-name ● ACTIVITY EXECUTETIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMACTIVITY EXECUTETIME HISTOGRAM TEMPLATEtemplate-name ● REQUEST EXECUTETIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMREQUEST EXECUTETIME HISTOGRAM TEMPLATEtemplate-name ● ACTIVITY ESTIMATEDCOST HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMACTIVITY ESTIMATEDCOST HISTOGRAM TEMPLATEtemplate-name ● ACTIVITY INTERARRIVALTIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMACTIVITY INTERARRIVALTIME HISTOGRAM TEMPLATEtemplate-name ● UOW LIFETIME HISTOGRAM TEMPLATE SYSDEFAULTHISTOGRAMUOW LIFETIME HISTOGRAM TEMPLATEtemplate-name ●
Notes:
  • 1 The DEGREE SCALEBACK DEFAULT option is valid only for a service subclass (SQLSTATE 5U043).
  • 2 The MAXIMUM DEGREE DEFAULT option is valid only for a service subclass (SQLSTATE 5U043).
  • 3 All COLLECT clauses except for COLLECT ACTIVITY DATA and COLLECT REQUEST METRICS are valid only for a service subclass.
  • 4 The COLLECT REQUEST METRICS clause is valid only for a service superclass.
  • 5 The HISTOGRAM TEMPLATE clauses are valid only for a service subclass.
  • 6 The DETAILS keyword is the minimum to be specified, followed by the option separated by a comma.

Description

service-class-name
Names the service class. This is a one-part name. It is an SQL identifier (either ordinary or delimited). If the service class is a service superclass, the service-class-name must not identify a service superclass that already exists in the catalog (SQLSTATE 42710). If the service class is a service subclass, the service-class-name must not identify a service subclass that already exists under the service superclass (SQLSTATE 42710). If the service class is a service subclass, the service-class-name must not be the same as its service superclass (SQLSTATE 42710). The name must not begin with the characters 'SYS' (SQLSTATE 42939).
UNDER service-superclass-name
Specifies that the service class is a subclass of service superclass service-superclass-name. If UNDER is not specified, the service class is a service superclass. The service-superclass-name must identify a service superclass that exists for the database (SQLSTATE 42704). The service superclass cannot be a default service class (SQLSTATE 5U029).
HARD CPU SHARES 1000 or HARD CPU SHARES integer-constant or SOFT CPU SHARES integer-constant
Specifies the number of shares of CPU resources that the workload manager (WLM) dispatcher allocates to this service class when work is executing within this service class. Valid values for the integer-constant are integers between 1 and 65535. The default is HARD CPU SHARES 1000, which allocates 1000 hard shares to this service class. Qualifying CPU SHARES with the keyword HARD, or specifying CPU SHARES without qualifying it with the keyword HARD or SOFT, indicates that hard CPU shares are to be allocated to this service class. Specifying the keyword SOFT indicates that soft CPU shares are to be allocated to this service class. To use hard and soft CPU shares with WLM dispatcher, you must enable the wlm_disp_cpu_shares database manager configuration parameter.
CPU LIMIT integer-constant or CPU LIMIT NONE
Specifies the maximum percentage of the CPU resources that the WLM dispatcher can assign to this service class. Valid values for the integer-constant are integers between 1 and 100. You can also specify CPU LIMIT NONE to indicate that there is no CPU limit.
DEGREE SCALEBACK DEFAULT or DEGREE SCALEBACK ON | OFF
Specifies whether work running in this service class may have its degree scaled back. Queries set to DEGREE ANY may have their actual runtime degree scaled back by the database manager based on current CPU loads.

Scaling back the degree for service classes running simple queries may result in less contention and improved throughput. Disabling degree scale back for service classes with complex queries can help ensure more consistent and predictable response times. A setting of DEFAULT means a service subclass inherits its DEGREE SCALEBACK setting from the parent superclass. The DEFAULT setting is only applicable to service subclasses. The default setting for a service superclass is ON. The default value for a service subclass is DEFAULT.

MAXIMUM DEGREE
Specifies the maximum runtime degree of parallelism for activities that are running in this service class.
DEFAULT
This service subclass inherits its maximum degree value from its parent superclass. This value is the default for a service subclass. This setting is applicable only to service subclasses.
NONE
This service class does not specify a maximum runtime degree for assigned applications. The actual runtime degree is determined as the lower of the value of max_querydegree configuration parameter, the value set by SET RUNTIME DEGREE command, the SQL statement compilation degree and the MAXIMUM DEGREE value set on the Workload. This is the default for a service superclass.
degree
Specifies the maximum degree of parallelism for this service class. Valid values are 1 to 32767. The actual runtime degree is determined as the lower of this degree, the value of max_querydegree configuration parameter, the value set by SET RUNTIME DEGREE command, the SQL statement compilation degree and the MAXIMUM DEGREE set on the Workload.
PREFETCH PRIORITY DEFAULT | HIGH | MEDIUM | LOW
This parameter controls the priority with which agents in the service class can submit their prefetch requests. Valid values are HIGH, MEDIUM, LOW, or DEFAULT (SQLSTATE 42615). HIGH, MEDIUM, and LOW mean that prefetch requests will be submitted to the high, medium, and low priority queues, respectively. Prefetchers empty the priority queue in order from high to low. Agents in the service class submit their prefetch requests at the PREFETCH PRIORITY level when the next activity begins. If PREFETCH PRIORITY is altered after a prefetch request is submitted, the request priority does not change. The default value is DEFAULT, which is internally mapped to MEDIUM for service superclasses. If DEFAULT is specified for a service subclass, it inherits the PREFETCH PRIORITY of its parent superclass.

PREFETCH PRIORITY cannot be altered for a default subclass (SQLSTATE 5U032).

OUTBOUND CORRELATOR NONE or OUTBOUND CORRELATOR string-constant
Specifies whether or not to associate threads from this service class to an external workload manager service class.

If OUTBOUND CORRELATOR is set to a string-constant for the service superclass and OUTBOUND CORRELATOR NONE is set for a service subclass, the service subclass inherits the OUTBOUND CORRELATOR of its parent. The default is OUTBOUND CORRELATOR NONE.

OUTBOUND CORRELATOR NONE
For a service superclass, specifies that there is no external workload manager service class association with this service class, and for a service subclass, specifies that the external workload manager service class association is the same as its parent.
OUTBOUND CORRELATOR string-constant
Specifies the string-constant that is to be used as a correlator to associate threads from this service class to an external workload manager service class. The external workload manager must be active (SQLSTATE 5U030). The external workload manager should be set up to recognize the value of string-constant.
BUFFERPOOL PRIORITY DEFAULT | HIGH | MEDIUM | LOW
This parameter controls the bufferpool priority of pages fetched by activities in this service class. Valid values are HIGH, MEDIUM, LOW or DEFAULT (SQLSTATE 42615). Pages fetched by activities in a service class with higher bufferpool priority are less likely to be swapped out than pages fetched by activities in a service class with lower bufferpool priority. The default value is DEFAULT, which is internally mapped to LOW for service superclasses. If DEFAULT is specified for a service subclass, it inherits the BUFFERPOOL PRIORITY from its parent superclass.

BUFFERPOOL PRIORITY cannot be altered for a default subclass (SQLSTATE 5U032).

COLLECT ACTIVITY DATA
Specifies that information about each activity that executes in this service class is to be sent to any active activities event monitor when the activity completes. The default is COLLECT ACTIVITY DATA NONE.
NONE
Specifies that activity data should not be collected for each activity that executes in this service class.
ON COORDINATOR MEMBER
Specifies that activity data is to be collected only at the coordinator member of the activity.
ON ALL MEMBERS
Specifies that activity data is to be collected at all members where the activity is processed. On remote members, a record for the activity may be captured multiple times as the activity comes and goes on those members. If the AND VALUES clause is specified, activity input values will be collected only for the members of the coordinator.
WITHOUT DETAILS
Specifies that data about each activity that executes in the service class is to be sent to any active activities event monitor, when the activity completes execution. Details about statement, compilation environment, and section environment data are not sent.
WITH
DETAILS
Specifies that statement and compilation environment data is to be sent to any active activities event monitor, for those activities that have them. Section environment data is not sent.
SECTION
Specifies that statement, compilation environment, section environment data, and section actuals are to be sent to any active activities event monitor for those activities that have them. DETAILS must be specified if SECTION is specified. Section actuals will be collected on any member where the activity data is collected.
INCLUDE ACTUALS BASE
Specifies that section actuals should also be collected on any partition where the activity data is collected. For section actuals to be collected, either INCLUDE ACTUALS clause must be specified or the section_actuals database configuration parameter must be set.

The effective setting for the collection of section actuals is the combination of the INCLUDE ACTUALS clause, the section_actuals database configuration parameter, and the <collectsectionactuals> setting specified on the WLM_SET_CONN_ENV routine. For example, if INCLUDE ACTUALS BASE is specified, yet the section_actuals database configuration parameter value is NONE and <collectsectionactuals> is set to NONE, then the effective setting for the collection of section actuals is BASE.

BASE specifies that the following should be enabled and collected during the activity's execution:
  • Basic operator cardinality counts
  • Statistics for each object referenced (DML statements only)
AND VALUES
Specifies that input data values are to be sent to any active activities event monitor, for those activities that have them. This data does not include SQL statements that are compiled by using the REOPT ALWAYS bind option.
COLLECT AGGREGATE ACTIVITY DATA
Specifies that aggregate activity data should be captured for this service class and sent to the statistics event monitor, if one is active. This information is collected periodically on an interval that is specified by the wlm_collect_int database configuration parameter. The default when COLLECT AGGREGATE ACTIVITY DATA is not specified is COLLECT AGGREGATE ACTIVITY DATA NONE. The default when COLLECT AGGREGATE ACTIVITY DATA is specified is COLLECT AGGREGATE ACTIVITY DATA BASE. The COLLECT AGGREGATE ACTIVITY DATA clause is valid only for a service subclass.
BASE
Specifies that basic aggregate activity data should be captured for this service class and sent to the statistics event monitor, if one is active. Basic aggregate activity data includes:
  • Estimated activity cost high watermark
  • Rows returned high watermark
  • Temporary table space usage high watermark
    Note: Only activities that have an SQLTEMPSPACE threshold applied to them participate in this high watermark.
  • Activity life time histogram
  • Activity queue time histogram
  • Activity execution time histogram
EXTENDED
Specifies that all aggregate activity data should be captured for this service class and sent to the statistics event monitor, if one is active. This includes all basic aggregate activity data plus:
  • Activity data manipulation language (DML) estimated cost histogram
  • Activity DML inter-arrival time histogram
NONE
Specifies that no aggregate activity data should be captured for this service class.
COLLECT AGGREGATE REQUEST DATA
Specifies that aggregate request data should be captured for this service class and sent to the statistics event monitor, if one is active. This information is collected periodically on an interval specified by the wlm_collect_int database configuration parameter. The default is COLLECT AGGREGATE REQUEST DATA NONE. The COLLECT AGGREGATE REQUEST DATA clause is valid only for a service subclass.
BASE
Specifies that basic aggregate request data should be captured for this service class and sent to the statistics event monitor, if one is active.
NONE
Specifies that no aggregate request data should be captured for this service class.
COLLECT AGGREGATE UNIT OF WORK DATA
Specifies that aggregate unit of work data is to be captured for this service class and sent to the statistics event monitor, if one is active. This information is collected periodically on an interval specified by the wlm_collect_int database configuration parameter. The default is COLLECT AGGREGATE UNIT OF WORK DATA NONE. The COLLECT AGGREGATE UNIT OF WORK DATA clause is valid only for a service subclass.
BASE
Specifies that basic aggregate unit of work data is to be captured for this service class and sent to the statistics event monitor, if one is active. Basic aggregate unit of work includes:
  • Unit of work lifetime histogram
NONE
Specifies that no aggregate unit of work data is to be collected for this service class.
COLLECT REQUEST METRICS
Specifies that monitor metrics should be collected for any request submitted by a connection that is associated with the specified service superclass and sent to the statistics and unit of work event monitors, if active. The default is COLLECT REQUEST METRICS NONE. The COLLECT REQUEST METRICS clause is valid only for a service superclass (SQLSTATE 50U44).
Note: The effective request metrics collection setting is the combination of the attribute specified by the COLLECT REQUEST METRICS clause on the service superclass associated with the connection submitting the request, and the mon_req_metrics database configuration parameter. If either the service superclass attribute or the configuration parameter has a value other than NONE, metrics will be collected for the request.
NONE
Specifies that no metrics will be collected for any request submitted by a connection associated with the service superclass.
BASE
Specifies that basic metrics will be collected for any request submitted by a connection associated with the service superclass.
EXTENDED
Specifies that basic aggregate request data should be captured for this service class and sent to the statistics event monitor, if one is active. In addition, specifies that the values for the following monitor elements should be determined with additional granularity:
  • total_section_time
  • total_section_proc_time
  • total_routine_user_code_time
  • total_routine_user_code_proc_time
  • total_routine_time
histogram-template-clause
Specifies the histogram templates to use when collecting aggregate activity data for activities executing in the service class. The HISTOGRAM TEMPLATE clause is valid only for a service subclass.
ACTIVITY LIFETIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the duration, in milliseconds, of database activities running in the service class during a specific interval. This time includes both time queued and time executing. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE ACTIVITY DATA clause is specified, with either the BASE or EXTENDED option.
ACTIVITY QUEUETIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the length of time, in milliseconds, that database activities running in the service class are queued during a specific interval. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE ACTIVITY DATA clause is specified, with either the BASE or EXTENDED option.
ACTIVITY EXECUTETIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the length of time, in milliseconds, that database activities running in the service class are executing during a specific interval. This time does not include the time spent queued. Activity execution time is collected in this histogram at the coordinator member only. The time does not include idle time. Idle time is the time between the execution of requests belonging to the same activity when no work is being done. An example of idle time is the time between the end of opening a cursor and the start of fetching from that cursor. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE ACTIVITY DATA clause is specified, with either the BASE or EXTENDED option. Only activities at nesting level 0 are considered for inclusion in the histogram.
REQUEST EXECUTETIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the length of time, in milliseconds, that database requests running in the service class are executing during a specific interval. This time does not include the time spent queued. Request execution time is collected in this histogram on each member where the request executes. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE REQUEST DATA clause is specified with the BASE option.
ACTIVITY ESTIMATEDCOST HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the estimated cost, in timerons, of DML activities running in the service class. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE ACTIVITY DATA clause is specified with the EXTENDED option. Only activities at nesting level 0 are considered for inclusion in the histogram.
ACTIVITY INTERARRIVALTIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the length of time, in milliseconds, between the arrival of one DML activity and the arrival of the next DML activity. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE ACTIVITY DATA clause is specified with the EXTENDED option.
UOW LIFETIME HISTOGRAM TEMPLATE template-name
Specifies the template that describes the histogram used to collect statistical data about the duration, in milliseconds, of units of work running in the service class during a specific interval. The default is SYSDEFAULTHISTOGRAM. This information is collected only when the COLLECT AGGREGATE UNIT OF WORK DATA clause is specified with the BASE option.
ENABLE or DISABLE
Specifies whether or not connections and activities can be mapped to the service class. The default is ENABLE.
ENABLE
Connections and activities can be mapped to the service class.
DISABLE
Connections and activities cannot be mapped to the service class. New connections or activities that are mapped to a disabled service class will be rejected (SQLSTATE 5U028). When a service superclass is disabled, its service subclasses are also disabled. When the service superclass is re-enabled, its service subclasses return to states that are defined in the system catalog. A default service class cannot be disabled (SQLSTATE 5U032).

Rules

  • The maximum number of service subclasses that can be created under a service superclass is 61 (SQLSTATE 5U027).
  • The maximum number of service superclasses that can be created for a database is 64 (SQLSTATE 5U027).
  • A workload management (WLM)-exclusive SQL statement must be followed by a COMMIT or a ROLLBACK statement (SQLSTATE 5U027). WLM-exclusive SQL statements are:
    • CREATE HISTOGRAM TEMPLATE, ALTER HISTOGRAM TEMPLATE, or DROP (histogram template)
    • CREATE SERVICE CLASS, ALTER SERVICE CLASS, or DROP (service class)
    • CREATE THRESHOLD, ALTER THRESHOLD, or DROP (threshold)
    • CREATE WORK ACTION SET, ALTER WORK ACTION SET, or DROP (work action set)
    • CREATE WORK CLASS SET, ALTER WORK CLASS SET, or DROP (work class set)
    • CREATE WORKLOAD, ALTER WORKLOAD, or DROP (workload)
    • GRANT (workload privileges) or REVOKE (workload privileges)
  • A WLM-exclusive SQL statement cannot be issued within a global transaction (SQLSTATE 51041) such as, for example, an XA transaction.

Notes

  • A default subclass, SYSDEFAULTSUBCLASS, is automatically created for every service superclass.
  • Only one uncommitted WLM-exclusive SQL statement at a time is allowed across all members. If an uncommitted WLM-exclusive SQL statement is executing, subsequent WLM-exclusive SQL statements will wait until the current WLM-exclusive SQL statement commits or rolls back.
  • Changes are written to the system catalog, but do not take effect until after a COMMIT statement, even for the connection that issues the statement.
  • Syntax alternatives: The following are supported for compatibility with previous versions of Db2® and with other database products. These alternatives are non-standard and should not be used.
    • DATABASE PARTITION can be specified in place of MEMBER, except when the DB2_ENFORCE_MEMBER_SYNTAX registry variable is set to ON.
    • DATABASE PARTITIONS can be specified in place of MEMBERS, except when the DB2_ENFORCE_MEMBER_SYNTAX registry variable is set to ON.

Examples

  • Example 1: Create a service superclass named PETSALES. The default subclass for PETSALES is automatically created.
       CREATE SERVICE CLASS PETSALES
  • Example 2: Create a service subclass named DOGSALES under service superclass PETSALES. Set service class DOGSALES as disabled.
       CREATE SERVICE CLASS DOGSALES UNDER PETSALES DISABLE
  • Example 3: Create a service superclass named BARNSALES with a prefetcher priority of LOW. The default subclass for BARNSALES is automatically created. Prefetch requests submitted by agents in the BARNSALES service class will go to the low priority prefetch queue.
       CREATE SERVICE CLASS BARNSALES PREFETCH PRIORITY LOW