CREATE EVENT MONITOR statement

The CREATE EVENT MONITOR statement defines a monitor that will record certain events that occur when using the database. The definition of each event monitor also specifies where the database should record the events.

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

>>-CREATE EVENT MONITOR--event-monitor-name--FOR---------------->

   .-,------------------------------------------------------------.   
   V                                                              |   
>----+-+-DATABASE---------------------------------------------+-+-+-->
     | +-TABLES-----------------------------------------------+ |     
     | +-DEADLOCKS--+---------------------------------------+-+ |     
     | |            '-WITH DETAILS--+---------------------+-' | |     
     | |                            '-HISTORY--+--------+-'   | |     
     | |                                       '-VALUES-'     | |     
     | +-TABLESPACES------------------------------------------+ |     
     | '-BUFFERPOOLS------------------------------------------' |     
     '-+-CONNECTIONS--+--+----------------------------+---------'     
       +-STATEMENTS---+  '-WHERE--| event-condition |-'               
       '-TRANSACTIONS-'                                               

>--WRITE TO--+-TABLE--| evm-group-info |---------+--●----------->
             +-PIPE--pipe-name-------------------+      
             '-FILE--path-name--| file-options |-'      

   .-MANUALSTART-.      
>--+-------------+--●------------------------------------------->
   '-AUTOSTART---'      

>--+----------------------------------------+--●---------------->
   '-ON DBPARTITIONNUM--db-partition-number-'      

   .-LOCAL--.      
>--+--------+--●-----------------------------------------------><
   '-GLOBAL-'      

event-condition

   .-AND | OR-----------------------------------------------------.   
   V                                                              |   
|----+-----+--+-+-APPL_ID---+--+-=---------+--comparison-string-+-+--|
     '-NOT-'  | +-AUTH_ID---+  |    (1)    |                    |     
              | '-APPL_NAME-'  +-<>--------+                    |     
              |                +->---------+                    |     
              |                |    (1)    |                    |     
              |                +->=--------+                    |     
              |                +-<---------+                    |     
              |                |    (1)    |                    |     
              |                +-<=--------+                    |     
              |                +-LIKE------+                    |     
              |                '-NOT--LIKE-'                    |     
              '-(--event-condition--)---------------------------'     

evm-group-info

|--●--+------------------------------------------------+--●----->
      | .-,------------------------------------------. |      
      | V                                            | |      
      '---evm-group--+-----------------------------+-+-'      
                     '-(--| target-table-info |--)-'          

   .-BUFFERSIZE--4-----.     .-BLOCKED----.      
>--+-------------------+--●--+------------+--●------------------|
   '-BUFFERSIZE--pages-'     '-NONBLOCKED-'      

target-table-info

   .-------------------------------------------------.   
   V  (2)   (3)                                      |   
|----------------+-TABLE--table-name---------------+-+----------|
                 +-IN--tablespace-name-------------+     
                 | .-PCTDEACTIVATE--100-----.      |     
                 +-+-PCTDEACTIVATE--integer-+------+     
                 +-TRUNC---------------------------+     
                 |                  .-,-------.    |     
                 |                  V         |    |     
                 '-+-INCLUDES-+--(----element-+--)-'     
                   '-EXCLUDES-'                          

file-options

      .-MAXFILES--NONE------------.      
|--●--+---------------------------+--●-------------------------->
      '-MAXFILES--number-of-files-'      

                                  .-BUFFERSIZE--4-----.      
>--+------------------------+--●--+-------------------+--●------>
   '-MAXFILESIZE--+-pages-+-'     '-BUFFERSIZE--pages-'      
                  '-NONE--'                                  

   .-BLOCKED----.     .-APPEND--.      
>--+------------+--●--+---------+--●----------------------------|
   '-NONBLOCKED-'     '-REPLACE-'      

1. Other forms of these operators are also supported.
2. Each clause can be specified only once.
3. 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.

DATABASE

Specifies that the event monitor records a database event when the last application disconnects from the database.

TABLES

Specifies that the event monitor records a table event for each active table when the last application disconnects from the database. For partitioned tables, a table event is recorded for each data partition of each active table. An active table is a table that has changed since the first connection to the database.

DEADLOCKS

Note: This option has been deprecated. Its use is no longer recommended and might be removed in a future release. Use the CREATE EVENT MONITOR FOR LOCKING statement to monitor lock-related events, such as lock timeouts, lock waits, and deadlocks.

Specifies that the event monitor records a deadlock event whenever a deadlock occurs.

WITH DETAILS

Specifies that the event monitor is to generate a more detailed deadlock connection event for each application that is involved in a deadlock. This additional detail includes:

• Information about the statement that the application was executing when the deadlock occurred, such as the statement text
• The locks held by the application when the deadlock occurred. In a partitioned database environment, this includes only those locks that are held on the database partition on which the application was waiting for its lock when the deadlock occurred. For partitioned tables, this includes the data partition identifier.

HISTORY

Specifies that the event monitor data will also include:

• The history of all statements in the current unit of work at the participating node (including WITH HOLD cursors opened in previous units of work). SELECT statements issued at the uncommitted read (UR) isolation level are not included in the statement history.
• The statement compilation environment for each SQL statement in binary format (if available)

VALUES

Specifies that the event monitor data will also include:

• The data values used as input variables for each SQL statement. These data values will not include LOB data, long data, structured type data, or XML data.

Only one of: DEADLOCKS, DEADLOCKS WITH DETAILS, DEADLOCKS WITH DETAILS HISTORY, or DEADLOCKS WITH DETAILS HISTORY VALUES can be specified in a single CREATE EVENT MONITOR statement (SQLSTATE 42613).

TABLESPACES

Specifies that the event monitor records a table space event for each table space when the last application disconnects from the database.

BUFFERPOOLS

Specifies that the event monitor records a buffer pool event when the last application disconnects from the database.

CONNECTIONS

Specifies that the event monitor records a connection event when an application disconnects from the database.

STATEMENTS

Specifies that the event monitor records a statement event whenever a SQL statement finishes executing.

TRANSACTIONS

Note: This option has been deprecated. Its use is no longer recommended and might be removed in a future release. Use the CREATE EVENT MONITOR FOR UNIT OF WORK statement to monitor transaction events.

Specifies that the event monitor records a transaction event whenever a transaction completes (that is, whenever there is a commit or rollback operation).

WHERE event-condition

Defines a filter that determines which connections cause a CONNECTION, STATEMENT or TRANSACTION event to occur. If the result of the event condition is TRUE for a particular connection, then that connection will generate the requested events.

This clause is a special form of the WHERE clause that should not be confused with a standard search condition.

To determine if an application will generate events for a particular event monitor, the WHERE clause is evaluated:

• For each active connection when an event monitor is first turned on
• Subsequently for each new connection to the database at connect time

The WHERE clause is not evaluated for each event.

If no WHERE clause is specified, all events of the specified event type will be monitored.

The event-condition must not exceed 32 678 bytes in length in the database code page (SQLSTATE 22001).

APPL_ID

Specifies that the application ID of each connection should be compared with the comparison-string in order to determine if the connection should generate CONNECTION, STATEMENT or TRANSACTION events (whichever was specified).

AUTH_ID

Specifies that the authorization ID of each connection should be compared with the comparison-string in order to determine if the connection should generate CONNECTION, STATEMENT or TRANSACTION events (whichever was specified).

APPL_NAME

Specifies that the application program name of each connection should be compared with the comparison-string in order to determine if the connection should generate CONNECTION, STATEMENT or TRANSACTION events (whichever was specified).

The application program name is the first 20 bytes of the application program file name, after the last path separator.

comparison-string

A string to be compared with the APPL_ID, AUTH_ID, or APPL_NAME of each application that connects to the database. comparison-string must be a string constant (that is, host variables and other string expressions are not permitted).

WRITE TO

Introduces 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.

evm-group-info

Defines the target table for a logical data group. This clause should be specified for each grouping that is to be recorded. However, if no evm-group-info clauses are specified, all groups for the event monitor type are recorded.

evm-group

Identifies the 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
Database	DB CONTROL1 DBMEMUSE
Tables	TABLE CONTROL1
Deadlocks	CONNHEADER DEADLOCK DLCONN CONTROL1
Deadlocks with details	CONNHEADER DEADLOCK DLCONN2 DLLOCK3 CONTROL1
Deadlocks with details history	CONNHEADER DEADLOCK DLCONN2 DLLOCK3 STMTHIST CONTROL1
Deadlocks with details history values	CONNHEADER DEADLOCK DLCONN2 DLLOCK3 STMTHIST STMTVALS CONTROL1
Tablespaces	TABLESPACE CONTROL1
Bufferpools	BUFFERPOOL CONTROL1
Connections	CONNHEADER CONN CONTROL1 CONNMEMUSE
Statements	CONNHEADER STMT SUBSECTION4 CONTROL1
Transactions	CONNHEADER XACT CONTROL1
1 Logical data groups dbheader (conn_time element only), start and overflow, are all written to the CONTROL group. The overflow group is written if the event monitor is non-blocked and events were discarded. 2 Corresponds to the DETAILED_DLCONN event. 3 Corresponds to the LOCK logical data groups that occur within each DETAILED_DLCONN event. 4 Created only for partitioned database environments.

target-table-info

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

• A derived table name is used (described below).
• A default table space is chosen (described below).
• All elements are included.
• PCTDEACTIVATE and TRUNC are not specified.

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 schema for the current authorization ID. 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

Defines the table space in which the table is to be created. If no table space name is provided, the table space is chosen using the same process as when a table is created without a table space name using CREATE TABLE.

PCTDEACTIVATE integer

If a table is being created in a 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. The default value is 100 (meaning that the event monitor deactivates when the table space becomes completely full). This option is ignored for SMS table spaces.

It is recommended that, when a target table space has auto-resize enabled, the PCTDEACTIVATE parameter be set to 100.

TRUNC

Specifies that the STMT_TEXT and STMT_VALUE_DATA columns are defined as VARCHAR(n), where n is the largest size that can fit into the table row. In this case, any data that is longer than n bytes is truncated. The following example illustrates how the value of n is calculated. Assume that:

• The table is created in a table space that uses 32K pages.
• The total length of all the other columns in the table equals 357 bytes.

In this case, the maximum row size for a table is 32677 bytes. Therefore, the element would be defined as VARCHAR(32316); that is, 32677 - 357 - 4. If TRUNC is not specified, the column will be defined as CLOB(2M). Note that STMT_TEXT is found in the STMT event group, the STMT_HISTORY event group, and the DLCONN event group (for deadlocks with details event monitors). STMT_VALUE_DATA is found in the DATA_VALUE event group.

INCLUDES

Specifies that the following elements are to be included in the table.

EXCLUDES

Specifies that the following elements are not to be included in the table.

element

Identifies a monitor element. Element information can be provided in one of the following forms:

• Specify no element information. In this case, all elements are included in the CREATE TABLE statement.
• Specify the elements to include in the form: INCLUDES (element1, element2, ..., elementn). Only table columns are created for these elements.
• Specify the elements to exclude in the form: EXCLUDES (element1, element2, ..., elementn). Only table columns are created for all elements except these.

Use the db2evtbl command to build a CREATE EVENT MONITOR statement that includes a complete list of elements for a group.

BUFFERSIZE pages

Specifies the size of the event monitor buffers (in units of 4K pages). Table event monitors insert all data from a buffer, and issues a COMMIT once the buffer has been processed. The larger the buffers, the larger the commit scope used by the event monitor. Highly active event monitors should have larger buffers than relatively inactive event monitors. When a monitor is started, two buffers of the specified size are allocated. Event monitors use double buffering to permit asynchronous I/O.

The default size of each buffer is 4 pages (two 16K buffers are allocated). The minimum size is 1 page. The maximum size of the buffers is limited by the size of the monitor heap, because the buffers are allocated from that heap. If many event monitors are being used at the same time, increase the size of the mon_heap_sz database manager configuration parameter.

BLOCKED

Specifies that each agent that generates an event should wait for an event buffer to be written out to disk if the agent determines that both event buffers are full. BLOCKED should be selected to guarantee no event data loss. This is the default option.

NONBLOCKED

Specifies that each agent that generates an event should not wait for the event buffer to be written out to disk if the agent determines that both event buffers are full. NONBLOCKED event monitors do not slow down database operations to the extent of BLOCKED event monitors. However, NONBLOCKED event monitors are subject to data loss on highly active systems.

PIPE

Specifies that the target for the event monitor data is a named pipe. The event monitor writes the data to the pipe in a single stream (that is, as if it were a single, infinitely long file). When writing the data to a pipe, an event monitor does not perform blocked writes. If there is no room in the pipe buffer, then the event monitor will discard the data. It is the monitoring application's responsibility to read the data promptly if it wishes to ensure no data loss.

pipe-name

The name of the pipe (FIFO on AIX®) to which the event monitor will write the data.

The naming rules for pipes are platform specific. On UNIX operating systems, pipe names are treated like file names. As a result, relative pipe names are permitted, and are treated like relative path-names (see path-name below). On Windows, however, there is a special syntax for a pipe name and, as a result, absolute pipe names are required.

The existence of the pipe will not be checked at event monitor creation time. It is the responsibility of the monitoring application to have created and opened the pipe for reading at the time that the event monitor is activated. If the pipe is not available at this time, then the event monitor will turn itself off, and will log an error. (That is, if the event monitor was activated at database start time as a result of the AUTOSTART option, then the event monitor will log an error in the system error log.) If the event monitor is activated via the SET EVENT MONITOR STATE SQL statement, then that statement will fail (SQLSTATE 58030).

FILE

Indicates that the target for the event monitor data is a file (or set of files). The event monitor writes out the stream of data as a series of 8 character numbered files, with the extension "evt". (for example, 00000000.evt, 00000001.evt, and 00000002.evt). The data should be considered to be one logical file even though the data is broken up into smaller pieces (that is, the start of the data stream is the first byte in the file 00000000.evt; the end of the data stream is the last byte in the file nnnnnnnn.evt).

The maximum size of each file can be defined as well as the maximum number of files. An event monitor will never split a single event record across two files. However, an event monitor may write related records in two different files. It is the responsibility of the application that uses this data to keep track of such related information when processing the event files.

path-name

The name of the directory in which the event monitor should write the event files data. The path must be known at the server; however, the path itself could reside on another database partition (for example, on a UNIX system, this might be an NFS mounted file). A string constant must be used when specifying the path-name.

The directory does not have to exist at CREATE EVENT MONITOR time. However, a check is made for the existence of the target path when the event monitor is activated. At that time, if the target path does not exist, an error (SQLSTATE 428A3) is raised.

If an absolute path (a path that starts with the root directory on AIX, or a disk identifier on Windows) is specified, the specified path will be the one used. If a relative path (a path that does not start with the root) is specified, then the path relative to the DB2EVENT directory in the database directory will be used.

It is possible to specify two or more event monitors that have the same target path. However, once one of the event monitors has been activated for the first time, and as long as the target directory is not empty, it will be impossible to activate any of the other event monitors.

file-options

Specifies the options for the file format.

MAXFILES NONE

Specifies that there is no limit to the number of event files that the event monitor will create. This is the default.

MAXFILES number-of-files

Specifies that there is a limit on the number of event monitor files that will exist for a particular event monitor at any time. Whenever an event monitor has to create another file, it will check to make sure that the number of .evt files in the directory is less than number-of-files. If this limit has already been reached, then the event monitor will turn itself off.

If an application removes the event files from the directory after they have been written, then the total number of files that an event monitor can produce can exceed number-of-files. This option has been provided to allow a user to guarantee that the event data will not consume more than a specified amount of disk space.

MAXFILESIZE pages

Specifies that there is a limit to the size of each event monitor file. Whenever an event monitor writes a new event record to a file, it checks that the file will not grow to be greater than pages (in units of 4K pages). If the resulting file would be too large, then the event monitor switches to the next file. The default for this option is:

• Windows - 200 4K pages
• UNIX - 1000 4K pages

The number of pages must be greater than at least the size of the event buffer in pages. If this requirement is not met, then an error (SQLSTATE 428A4) is raised.

MAXFILESIZE NONE

Specifies that there is no set limit on a file's size. If MAXFILESIZE NONE is specified, then MAXFILES 1 must also be specified. This option means that one file will contain all of the event data for a particular event monitor. In this case the only event file will be 00000000.evt.

BUFFERSIZE pages

Specifies the size of the event monitor buffers (in units of 4K pages). All event monitor file I/O is buffered to improve the performance of the event monitors. The larger the buffers, the less I/O will be performed by the event monitor. Highly active event monitors should have larger buffers than relatively inactive event monitors. When the monitor is started, two buffers of the specified size are allocated. Event monitors use double buffering to permit asynchronous I/O.

The default size of each buffer is 4 pages (two 16K buffers are allocated). The minimum size is 1 page. The maximum size of the buffers is limited by the value of the MAXFILESIZE parameter, as well as the size of the monitor heap, because the buffers are allocated from that heap. If many event monitors are being used at the same time, increase the size of the mon_heap_sz database manager configuration parameter.

Event monitors that write their data to a pipe also have two internal (non-configurable) buffers that are each 1 page in size. These buffers are also allocated from the monitor heap (MON_HEAP). For each active event monitor that has a pipe target, increase the size of the database heap by 2 pages.

BLOCKED

Specifies that each agent that generates an event should wait for an event buffer to be written out to disk if the agent determines that both event buffers are full. BLOCKED should be selected to guarantee no event data loss. This is the default option.

NONBLOCKED

Specifies that each agent that generates an event should not wait for the event buffer to be written out to disk if the agent determines that both event buffers are full. NONBLOCKED event monitors do not slow down database operations to the extent of BLOCKED event monitors. However, NONBLOCKED event monitors are subject to data loss on highly active systems.

APPEND

Specifies that if event data files already exist when the event monitor is turned on, then the event monitor will append the new event data to the existing stream of data files. When the event monitor is reactivated, it will resume writing to the event files as if it had never been turned off. APPEND is the default option.

The APPEND option does not apply at CREATE EVENT MONITOR time, if there is existing event data in the directory where the newly created event monitor is to write its event data.

REPLACE

Specifies that if event data files already exist when the event monitor is turned on, then the event monitor will erase all of the event files and start writing data to file 00000000.evt.

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. This is the default.

AUTOSTART

Specifies that the event monitor is to be automatically activated whenever the database partition on which the event monitor runs is activated.

ON DBPARTITIONNUM db-partition-number

Specifies the database partition on which a file or pipe event monitor is to run. When the monitoring scope is defined as LOCAL, data is only collected on the specified partition. When the monitoring scope is defined as GLOBAL, all database partitions collect data and report to the database partition with the specified number. The I/O component will physically run on the specified database partition, writing records to the specified file or pipe.

This clause is not valid for table event monitors. In a partitioned database environment, write-to-table event monitors will run and write events on all database partitions where table spaces for target tables are defined.

If this clause is not specified, the currently connected database partition number (for the application) is used.

LOCAL

The event monitor reports only on the database partition that is running. It gives a partial trace of the database activity. This is the default.

This clause is not valid for table event monitors.

GLOBAL

The event monitor reports on all database partitions. For a partitioned database, only DEADLOCKS event monitors can be defined as GLOBAL.

This clause is not valid for table event monitors.

Rules

• Each of the event types (DATABASE, TABLES, DEADLOCKs,...) can only be specified once in a particular event monitor definition.

Notes

• Event monitor definitions are recorded in the SYSCAT.EVENTMONITORS catalog view. The events themselves are recorded in the SYSCAT.EVENTS catalog view. The names of target tables are recorded in the SYSCAT.EVENTTABLES catalog view.
• There is a performance impact when using DEADLOCKS WITH DETAILS rather than DEADLOCKS. When a deadlock occurs, the database manager requires extra time to record the extra deadlock information.
• A CONNHEADER event is normally written whenever a connection is established. However, if an event monitor is created only for DEADLOCKS WITH DETAILS, a CONNHEADER event will only be written the first time that the connection participates in a deadlock.
• In a database with multiple database partitions, the ON DBPARTITIONNUM clause can be used with FILE and PIPE event monitors having a DEADLOCKS event type to indicate where the event monitor itself should reside; information from other database partitions, if relevant, is sent to that location for processing.
• In a database with multiple database partitions, a deadlock event monitor will receive information about applications that have locks participating in the deadlock from all the database partitions on which those participating locks existed. If the database partition to which the application is connected (the application coordinator partition) is not one of the participating database partitions, no information about a deadlock event will be received from that database partition.
• The BUFFERSIZE parameter restricts the size of STMT, STMT_HISTORY, DATA_VALUE, and DETAILED_DLCONN events. If a STMT or a STMT_HISTORY event cannot fit within a buffer, it is truncated by truncating statement text. If a DETAILED_DLCONN event cannot fit within a buffer, it is truncated by removing locks. If it still cannot fit, statement text is truncated. If a DATA_VAL event cannot fit within a buffer, the data value is truncated.

  Event monitors WITH DETAILS HISTORY VALUES (and, to a lesser extent, WITH DETAILS HISTORY) use a significant amount of monitor heap space to track statements and their data values. For more information, see the description of the mon_heap_sz database manager configuration parameter.

• If the database partition on which the event monitor is to run is not active, event monitor activation occurs when that database partition next activates.
• After an event monitor is activated, it behaves like an autostart event monitor until that event monitor is explicitly deactivated or the instance is recycled. That is, if an event monitor is active when a database partition is deactivated, and that database partition is subsequently reactivated, the event monitor is also explicitly reactivated.
• Write to table event monitors: General notes:
  • All target tables are created when the CREATE EVENT MONITOR statement executes.
  • If the creation of a table fails for any reason, an error is passed back to the application program, and the CREATE EVENT MONITOR statement fails.
  • A target table can only be used by one event monitor. During CREATE EVENT MONITOR processing, if a target table is found to have already been defined for use by another event monitor, the CREATE EVENT MONITOR 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.
  • During CREATE EVENT MONITOR processing, if a table already exists, but is not defined for use by another event monitor, no table is created, and processing continues. A warning is passed back to the application program.
  • Any table spaces must exist before the CREATE EVENT MONITOR statement is executed. The CREATE EVENT MONITOR statement does not create table spaces.
  • If specified, the LOCAL and GLOBAL keywords are ignored. With WRITE TO TABLE event monitors, an event monitor output process or thread is started on each database partition in the instance, and each of these processes reports data only for the database partition on which it is running.
  • The following event types from the flat monitor log file or pipe format are not recorded by write to table event monitors:
    • LOG_STREAM_HEADER
    • LOG_HEADER
    • DB_HEADER (Elements db_name and db_path are not recorded. The element conn_time is recorded in CONTROL.)
  • In a partitioned database environment, data is only written to target tables on the database partitions where their table spaces exist. If a table space for a target 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, by creating a table space that exists only on certain database partitions.

    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.

  • Users must manually prune all target tables.
  Table Columns:
  • Column names in a table match an event monitor element identifier. Any event monitor element that does not have a corresponding target table column is ignored.
  • Use the db2evtbl command to build a CREATE EVENT MONITOR command that includes a complete list of elements for a group.
  • The types of columns being used for monitor elements correlate to the following mapping:

    SQLM_TYPE_STRING                     CHAR[n], VARCHAR[n] or CLOB(n)
                                         (If the data in the event monitor
                                         record exceeds n bytes,
                                         it is truncated.)
    SQLM_TYPE_U8BIT and SQLM_TYPE_8BIT   SMALLINT, INTEGER or BIGINT
    SQLM_TYPE_16BIT and SQLM_TYPE_U16BIT SMALLINT, INTEGER or BIGINT
    SQLM_TYPE_32BIT and SQLM_TYPE_U32BIT INTEGER or BIGINT
    SQLM_TYPE_U64BIT and SQLM_TYPE_64BIT BIGINT
    sqlm_timestamp                       TIMESTAMP
    sqlm_time(elapsed time)              BIGINT
    sqlca:
      sqlerrmc                           VARCHAR[72]
      sqlstate                           CHAR[5]
      sqlwarn                            CHAR[11]
      other fields                       INTEGER or BIGINT

  • Columns are defined to be NOT NULL.
  • Because the performance of tables with CLOB columns is inferior to tables that have VARCHAR columns, consider using the TRUNC keyword when specifying the STMT evm-group value (or the DLCONN evm-group value, if using the DEADLOCKS WITH DETAILS event type).
  • Unlike other target tables, the columns in the CONTROL table do not match monitor element identifiers. Columns are defined as follows:

    Column Name      Data Type     Nullable  Description
    -----------      ---------     --------  -----------
    PARTITION_KEY    INTEGER       N         Distribution key (partitioned
                                             database only)
    PARTITION_NUMBER INTEGER       N         Database partition number
                                             (partitioned database only)
    EVMONNAME        VARCHAR(128)  N         Name of the event monitor
    MESSAGE          VARCHAR(128)  N         Describes the nature of the MESSAGE_TIME column.
                                             For more details see,
                                             message - Control Table Message monitor element
    MESSAGE_TIME     TIMESTAMP     N         Timestamp

  • In a partitioned database environment, the first column of each table is named PARTITION_KEY, is NOT NULL, and is of type INTEGER. This column is used as the distribution key for the table. The value of this column is chosen so that each event monitor process inserts data into the database partition on which the process is running; that is, insert operations are performed locally on the database partition where the event monitor process is running. On any database partition, the PARTITION_KEY field will contain the same value. This means that if a database partition is dropped and data redistribution is performed, all data on the dropped database partition will go to one other database partition instead of being evenly distributed. Therefore, before removing a database partition, consider deleting all table rows on that database partition.
  • In a partitioned database environment, a column named PARTITION_NUMBER can be defined for each table. This column is NOT NULL and is of type INTEGER. It contains the number of the database partition on which the data was inserted. Unlike the PARTITION_KEY column, the PARTITION_NUMBER column is not mandatory. The PARTITION_NUMBER column is not allowed in a non-partitioned database environment.
  Table Attributes:
  • Default table attributes are used. Besides distribution key (partitioned databases only), no extra options are specified when creating tables.
  • Indexes on the table can be created.
  • Extra table attributes (such as volatile, RI, triggers, constraints, and so on) can be added, but the event monitor process (or thread) will ignore them.
  • If "not logged initially" is added as a table attribute, it is turned off at the first COMMIT, and is not set back on.
  Event Monitor Activation:
  • When an event monitor activates, all target table names are retrieved from the SYSCAT.EVENTTABLES catalog view.
  • In a partitioned database environment, activation processing occurs on every database partition of the instance. On a particular database partition, activation processing determines the table spaces and database partition groups for each target table. The event monitor only activates on a database partition if at least one target table exists on that database partition. Moreover, if some target table is not found on a database partition, that target table is flagged so that data destined for that table is dropped during runtime processing.
  • If a target table does not exist when the event monitor activates (or, in a partitioned database environment, if the table space does not reside on a database partition), activation continues, and data that would otherwise be inserted into this table is ignored.
  • Activation processing validates each target table. If validation fails, activation of the event monitor fails, and messages are written to the administration log.
  • During activation in a partitioned database environment, the CONTROL table rows for FIRST_CONNECT and EVMON_START are only inserted on the catalog database partition. This requires that the table space for the control table exist on the catalog database partition. If it does not exist on the catalog database partition, these inserts are not performed.
  • In a partitioned database environment, if a partition is not yet active when a write to table event monitor is activated, the event monitor will be activated the next time that partition is activated.
  Run Time:
  • An event monitor runs with DATAACCESS authority.
  • If, while an event monitor is active, an insert operation into a target table fails:
    • Uncommitted changes are rolled back.
    • A message is written to the administration log.
    • The event monitor is deactivated.
  • If an event monitor is active, it performs a local COMMIT when it has finished processing an event monitor buffer.
  • In a partitioned database environment, the actual statement text, which can be up to 65 535 bytes in length, is only stored (in the STMT or DLCONN table) by the event monitor process running on the application coordinator database partition. On other database partitions, this value has zero length.
  • In a non-partitioned database environment, all write to table event monitors are deactivated when the last application terminates (and the database has not been explicitly activated). In a partitioned database environment, write to table event monitors are deactivated when the catalog partition deactivates.
  • The DROP EVENT MONITOR statement does not drop target tables.
  • Whenever a write-to-table event monitor activates, it will acquire IN table locks on each target table in order to prevent them from being modified while the event monitor is active. Table locks are maintained on all tables while the event monitor is active. If exclusive access is required on any of the target tables (for example, when a utility is to be run), first deactivate the event monitor to release the table locks before attempting such access.
• 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.
  • NODE can be specified in place of DBPARTITIONNUM
  • Commas can be used to separate multiple options in the target-table-info clause.

Examples

   CREATE EVENT MONITOR SMITHPAY
     FOR DATABASE, STATEMENTS
     WHERE APPL_NAME = 'PAYROLL' AND AUTH_ID = 'JSMITH'
     WRITE TO FILE '/home/jsmith/event/smithpay'
     MAXFILES 25
     MAXFILESIZE 1024
     NONBLOCKED
     APPEND

   CREATE EVENT MONITOR DEADLOCK_EVTS
     FOR DEADLOCKS
     WRITE TO FILE 'DLOCKS'
     MAXFILES 1
     MAXFILESIZE NONE
     AUTOSTART

   CREATE EVENT MONITOR DB_APPLS
     FOR CONNECTIONS
     WRITE TO PIPE '/home/jsmith/applpipe'

   CREATE EVENT MONITOR FOO
     FOR STATEMENTS
     WRITE TO TABLE

   CREATE EVENT MONITOR BAR
     FOR STATEMENTS, TRANSACTIONS
     WRITE TO TABLE
     STMT(TABLE MYDEPT.MYSTMTINFO IN MYTABLESPACE
       INCLUDES(ROWS_READ, ROWS_WRITTEN, STMT_TEXT)),
     STMT(TABLE MYDEPT.MYSTMTINFO IN MYTABLESPACE
       EXCLUDES(START_TIME, STOP_TIME, PARTIAL_RECORD)),
     XACT