CREATE EVENT MONITOR (unit of work) statement

Invocation

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

Authorization

Syntax

formatted-event-table-info

target-table-options

Notes:

• ¹ Each table option can be specified a maximum of one time (SQLSTATE 42613).
• ² Clauses can be separated with a space or a comma.

Description

event-monitor-name

Name of the event monitor. This is a one-part name. It is an SQL identifier (either ordinary or delimited). The event-monitor-name must not identify an event monitor that already exists in the catalog (SQLSTATE 42710).

FOR

Introduces the type of event to record.

UNIT OF WORK

Specifies that this passive event monitor will record an event whenever a unit of work is completed (that is, whenever there is a commit or rollback).

The creation of the unit of work event monitor does not indicate that the unit of work data will be collected immediately. The actual unit of work event of interest is controlled at the workload level.

WRITE TO

Specifies the target for the data.

TABLE

Indicates that the target for the event monitor data is a set of database tables. The event monitor separates the data stream into one or more logical data groups and inserts each group into a separate table. Data for groups having a target table is kept, whereas data for groups not having a target table is discarded. Each monitor element contained within a group is mapped to a table column with the same name. Only elements that have a corresponding table column are inserted into the table. Other elements are discarded.

formatted-event-table-info

Defines the target formatted event tables for the event monitor. This clause should specify each grouping that is to be recorded. However, if no evm-group clauses are specified, all groups for the event monitor type are recorded.

For more information about logical data groups, see Logical data groups and event monitor output tables .

evm-group

Identifies a logical data group for which a target table is being defined. The value depends upon the type of event monitor, as shown in the following table:

Type of Event Monitor	evm-group Value
Unit of work	UOW UOW_METRICS UOW_PACKAGE_LIST UOW_EXECUTABLE_LIST CONTROL

UNFORMATTED EVENT TABLE

Specifies that the target for the event monitor is an unformatted event table. The unformatted event table is used to store collected unit of work event monitor data. Data is stored in its original binary format within an inlined BLOB column. The BLOB column can contain multiple binary records of different types. The data in the BLOB column is not in a readable format and requires conversion, through use of the db2evmonfmt Java™-based tool, EVMON_FORMAT_UE_TO_XML table function, or EVMON_FORMAT_UE_TO_TABLES procedure, into a consumable format such as an XML document or a relational table.

target-table-options

Identifies options for the target table. If a value for target-table-options is not specified, CREATE EVENT MONITOR processing proceeds as follows:

• A derived table name is used (as explained in the description for TABLE table-name).
• A default table space is chosen using the same process as when a table is created without a table space name using CREATE TABLE.
• PCTDEACTIVATE is set to 100.

TABLE table-name

Specifies the name of the target table. The target table must be a non-partitioned table. If the name is unqualified, the table schema defaults to the value in the CURRENT SCHEMA special register. For an unformatted event table if a name is not provided, the unqualified name is equal to the event-monitor-name, that is, the unformatted event table will be named after the event monitor. For a formatted event table if no name is provided, the unqualified name is derived from evm-group and event-monitor-name as follows:

   substring(evm-group CONCAT '_'
     CONCAT event-monitor-name,1,128)

IN tablespace-name

Specifies the table space in which the table is to be created. The CREATE EVENT MONITOR FOR UNIT OR WORK statement does not create table spaces.

If a table space name is not provided, the table space is chosen using the same process as when a table is created without a table space name using CREATE TABLE.

Since the page size affects the INLINE LOB lengths used, consider specifying a table space with as large a page size as possible in order to improve the INSERT performance of the event monitor.

PCTDEACTIVATE integer

If a table for the event monitor is being created in an automatic storage (non-temporary) or DMS table space, the PCTDEACTIVATE parameter specifies how full the table space must be before the event monitor automatically deactivates. The specified value, which represents a percentage, can range from 0 to 100, where 100 means that the event monitor deactivates when the table space becomes completely full. The default value assumed is 100 if PCTDEACTIVATE is not specified. This option is ignored for SMS table spaces.

Important: If the target table space has auto-resize enabled, set PCTDEACTIVATE parameter to 100. Alternatively, omit this clause entirely to have the default of 100 apply. Otherwise, the event monitor might deactivate unexpectedly if the table space reaches the threshold specified by PCTDEACTIVTATE before the table space is automatically resized.

AUTOSTART

Specifies that the event monitor is to be automatically activated whenever the database partition on which the event monitor runs is activated. This is the default behavior of the unit of work event monitor.

MANUALSTART

Specifies that the event monitor must be activated manually using the SET EVENT MONITOR STATE statement. After a MANUALSTART event monitor has been activated, it can be deactivated only by using the SET EVENT MONITOR STATE statement or by stopping the instance.

Notes

• The table is created when the CREATE EVENT MONITOR FOR UNIT OF WORK statement executes, if it doesn't already exist.
• During CREATE EVENT MONITOR FOR UNIT OF WORK processing, if a table is found to have already been defined for use by another event monitor, the CREATE EVENT MONITOR FOR UNIT OF WORK statement fails, and an error is passed back to the application program. A table is defined for use by another event monitor if the table name matches a value found in the SYSCAT.EVENTTABLES catalog view. If the table exists and is not defined for use by another event monitor, then no table is created, any other table target-table-options parameters are ignored, and processing continues. A warning is passed back to the application program.
• Dropping the event monitor will not drop any tables. Any associated tables must be manually dropped after the event monitor is dropped.
• Lock event data is not automatically pruned from either unformatted event tables or regular tables created by this event monitor. An option for pruning data from UE tables is available when using the EVMON_FORMAT_UE_TO_TABLES procedure. For event monitors that write to regular tables, event data must be pruned manually.
• For unformatted event tables event data is inserted into the table into an inlined BLOB data column. Normally, BLOB data is stored in a separate LOB table space and can experience additional performance overhead as a result. When inlined into the data page of the base table, the BLOB data does not experience this overhead. The database manager will automatically inline the BLOB data portion of an unformatted event table record if the size of the BLOB data is less than the table space page size minus the record prefix. Therefore to achieve high efficiency and application throughput, it is suggested that you create the event monitor in as large a table space as possible up to and including a 32 KB table space and associated bufferpool.
• Create only one unit of work event monitor per database and not create multiple unit of work event monitors on the same database.
• In a partitioned database environment, data is written only to target tables on the database partitions where their table spaces exist. If a table space for a target unformatted event table does not exist on some database partition, data for that target table is ignored. This behavior allows users to choose a subset of database partitions for monitoring to be chosen, by creating a table space that exists only on certain database partitions.
• In a multi-member environment, data is only written to target tables on the member where work occurs within the unit of work.
• In a partitioned database environment, if some target tables do not reside on a database partition, but other target tables do reside on that same database partition, only the data for the target tables that do reside on that database partition is recorded.
• The unit of work event monitor is not affected by the unit or work event monitor switch. The unit of work event monitor switch is not changed when a unit or work event monitor is created, and the contents of the unit or work event monitor are not affected by changes to the unit of work event monitor switch.
• The FLUSH EVENT MONITOR statement is not applicable to this event monitor and will have no effect when issued against it.
• Creation of the unit of work event monitor does not cause events to be written to the event monitor. The unit of work event monitor must be activated with SET EVENT MONITOR STATE, and the unit of work data must be collected by either altering the appropriate workload to specify COLLECT UNIT OF WORK DATA or setting the mon_uow_data database configuration parameter to a value other than NONE.
• When using unformatted event tables, create the unit of work event monitor in a table space with at least 8 KB page size to ensure that the event data is contained within the inlined BLOB column of the unformatted event table. If the BLOB column is not inlined, then the performance of writing and reading the events to the unformatted event table might not be efficient.

Examples

• Example 1: This example creates a unit of work event monitor UOWEVMON that collects data for unit of work events that occur on the database of creation, and writes data tables using default table names:

     CREATE EVENT MONITOR UOWEVMON
       FOR UNIT OF WORK
       WRITE TO TABLE 

  This event monitor writes its output to the following tables:

  • UOW_UOWEVMON
  • UOW_METRICS_UOWEVMON
  • UOW_PACKAGE_LIST_UOWEVMON
  • UOW_EXECUTABLE_LIST_UOWEVMON
  • UOW_CONTROL_UOWEVMON

  Note: Whether the tables for package list and executable list information are populated with data is dependent on whether you specify that that data is to be collected. You control the collection of this data is using the mon_uow_pkglist or mon_uow_execlist configuration parameters, or with the appropriate COLLECT UNIT OF WORK DATA clause on the CREATE or ALTER WORKLOAD statements.
• Example 2: This example creates a unit of work event monitor UOWEVMON that will collect unit of work events that occur on the database of creation and store it in the unformatted event table GREG.UOWEVENTS.

     CREATE EVENT MONITOR UOWEVMON
       FOR UNIT OF WORK
       WRITE TO UNFORMATTED EVENT TABLE (TABLE GREG.UOWEVENTS)

• Example 3: This example creates a unit of work event monitor UOWEVMON that will collect unit of work events that occur on the database of creation and store it in the unformatted event table GREG.UOWEVENTS in table space APPSPACE. The event monitor will deactivate when the table space becomes 85% full.

     CREATE EVENT MONITOR UOWEVMON
       FOR UNIT OF WORK
       WRITE TO UNFORMATTED EVENT TABLE 
          (TABLE GREG.UOWEVENTS IN APPSPACE PCTDEACTIVATE 85)