DB2 Version 9.7 for Linux, UNIX, and Windows

SNAPLOCKWAIT administrative view and SNAP_GET_LOCKWAIT table function - Retrieve lockwait logical data group snapshot information

Note: This administrative view and table function have been deprecated and replaced by the MON_LOCKWAITS administrative view - Retrieve metrics for applications that are waiting to obtain locks and the MON_GET_APPL_LOCKWAIT table function - get information about locks for which an application is waiting, MON_GET_LOCKS table function - list all locks in the currently connected database, and MON_FORMAT_LOCK_NAME table function - format the internal lock name and return details.

The SNAPLOCKWAIT administrative view and the SNAP_GET_LOCKWAIT table function return snapshot information about lock waits, in particular, the lockwait logical data group.

SNAPLOCKWAIT administrative view

This administrative view allows you to retrieve lockwait logical data group snapshot information for the currently connected database.

Used with the SNAPLOCK administrative view, the SNAPLOCKWAIT administrative view provides information equivalent to the GET SNAPSHOT FOR LOCKS ON database-alias CLP command.

The schema is SYSIBMADM.

Refer to Table 1 for a complete list of information that can be returned.

Authorization

One of the following authorizations is required:

SELECT privilege on the SNAPLOCKWAIT administrative view
CONTROL privilege on the SNAPLOCKWAIT administrative view
DATAACCESS authority

In addition, one of the following privileges or authorities is also required:

EXECUTE privilege on the SNAP_GET_LOCKWAIT table function
DATAACCESS authority

In addition, to access snapshot monitor data, one of the following authorities is also required:

SYSMON
SYSCTRL
SYSMAINT
SYSADM

Example

Retrieve lock wait information about database partition 0 for the currently connected database.

SELECT AGENT_ID, LOCK_MODE, LOCK_OBJECT_TYPE, AGENT_ID_HOLDING_LK,
   LOCK_MODE_REQUESTED FROM SYSIBMADM.SNAPLOCKWAIT 
   WHERE DBPARTITIONNUM = 0

The following example is a sample output from this query.

AGENT_ID     LOCK_MODE LOCK_OBJECT_TYPE ...
--------...- --------- ---------------- ...
           7 IX        TABLE            ...
                                           
  1 record(s) selected.

Output from this query (continued).

... AGENT_ID_HOLDING_LK  LOCK_MODE_REQUESTED
... -------------------- -------------------
...                   12 IS

SNAP_GET_LOCKWAIT table function

The SNAP_GET_LOCKWAIT table function returns the same information as the SNAPLOCKWAIT administrative view, but allows you to retrieve the information for a specific database on a specific database partition, aggregate of all database partitions or all database partitions.

Used with the SNAP_GET_LOCK table function, the SNAP_GET_LOCKWAIT table function provides information equivalent to the GET SNAPSHOT FOR LOCKS ON database-alias CLP command.

Refer to Table 1 for a complete list of information that can be returned.

Syntax


>>-SNAP_GET_LOCKWAIT--(--dbname--+------------------+--)-------><
                                 '-, dbpartitionnum-'

The schema is SYSPROC.

Table function parameters

dbname: An input argument of type VARCHAR(128) that specifies a valid database name in the same instance as the currently connected database. Specify a database name that has a directory entry type of either "Indirect" or "Home", as returned by the LIST DATABASE DIRECTORY command. Specify a null value or empty string to take the snapshot from the currently connected database.
dbpartitionnum: An optional input argument of type INTEGER that specifies a valid database partition number. Specify -1 for the current database partition, or -2 for an aggregate of all active database partitions. If dbname is not set to NULL and dbpartitionnum is set to NULL, -1 is set implicitly for dbpartitionnum. If this input option is not used, that is, only dbname is provided, data is returned from all active database partitions. An active database partition is a partition where the database is available for connection and use by applications.

If both dbname and dbpartitionnum are set to NULL, an attempt is made to read data from the file created by SNAP_WRITE_FILE procedure. Note that this file could have been created at any time, which means that the data might not be current. If a file with the corresponding snapshot API request type does not exist, then the SNAP_GET_LOCKWAIT table function takes a snapshot for the currently connected database and database partition number.

Authorization

One of the following authorizations is required:

EXECUTE privilege on the SNAP_GET_LOCKWAIT table function
DATAACCESS authority

In addition, to access snapshot monitor data, one of the following authorities is also required:

SYSMON
SYSCTRL
SYSMAINT
SYSADM

Example

Retrieve lock wait information about current database partition for the currently connected database.

SELECT AGENT_ID, LOCK_MODE, LOCK_OBJECT_TYPE, AGENT_ID_HOLDING_LK,
   LOCK_MODE_REQUESTED FROM TABLE(SNAP_GET_LOCKWAIT('',-1)) AS T

The following example is a sample output from this query.

AGENT_ID      LOCK_MODE  LOCK_OBJECT_TYPE   ...
--------...-- ---------- ------------------ ...
           12 X          ROW_LOCK           ...
                                               
1 record(s) selected.

Output from this query (continued).

... AGENT_ID_HOLDING_LK  LOCK_MODE_REQUESTED
... -------------------- -------------------
...                    7 X

Usage note

To see lock wait information, you must first turn on the default LOCK monitor switch in the database manager configuration. To have the change take effect immediately explicitly attach to the instance using CLP and then issue the CLP command:

  UPDATE DATABASE MANAGER CONFIGURATION CLP USING DFT_MON_LOCK ON

The default setting can also be turned on through the ADMIN_CMD stored procedure. For example:

CALL SYSPROC.ADMIN_CMD('update dbm cfg using DFT_MON_LOCK ON')

If the ADMIN_CMD stored procedure is used or if the clp command is used without having previously attached to the instance, the instance must be recycled before the change takes effect.

Information returned

Table 1. Information returned by the SNAPLOCKWAIT administrative view and the SNAP_GET_LOCKWAIT table function
Column name	Data type	Description or corresponding monitor element
SNAPSHOT_TIMESTAMP	TIMESTAMP	snapshot_timestamp - Snapshot timestamp monitor element
AGENT_ID	BIGINT	agent_id - Application handle (agent ID)
SUBSECTION_NUMBER	BIGINT	ss_number - Subsection number
LOCK_MODE	VARCHAR(10)	lock_mode - Lock mode . This interface returns a text identifier based on the defines in sqlmon.h and is one of: IN IS IX NON (if no lock) NS NW S SIX U X Z
LOCK_OBJECT_TYPE	VARCHAR(18)	lock_object_type - Lock object type waited on . This interface returns a text identifier based on the defines in sqlmon.h and is one of: AUTORESIZE_LOCK AUTOSTORAGE_LOCK BLOCK_LOCK EOT_LOCK INPLACE_REORG_LOCK INTERNAL_LOCK INTERNALB_LOCK INTERNALC_LOCK INTERNALJ_LOCK INTERNALL_LOCK INTERNALO_LOCK INTERNALQ_LOCK INTERNALP_LOCK INTERNALS_LOCK INTERNALT_LOCK INTERNALV_LOCK KEYVALUE_LOCK ROW_LOCK SYSBOOT_LOCK TABLE_LOCK TABLE_PART_LOCK TABLESPACE_LOCK XML_PATH_LOCK
AGENT_ID_HOLDING_LK	BIGINT	agent_id_holding_lock - Agent ID holding lock
LOCK_WAIT_START_TIME	TIMESTAMP	lock_wait_start_time - Lock wait start timestamp
LOCK_MODE_REQUESTED	VARCHAR(10)	lock_mode_requested - Lock mode requested . This interface returns a text identifier based on the defines in sqlmon.h and is one of: IN IS IX NON (if no lock) NS NW S SIX U X Z
LOCK_ESCALATION	SMALLINT	lock_escalation - Lock escalation
TABNAME	VARCHAR(128)	table_name - Table name
TABSCHEMA	VARCHAR(128)	table_schema - Table schema name
TBSP_NAME	VARCHAR(128)	tablespace_name - Table space name
APPL_ID_HOLDING_LK	VARCHAR(128)	appl_id_holding_lk - Application ID holding lock
LOCK_ATTRIBUTES	VARCHAR(128)	lock_attributes - Lock attributes . This interface returns a text identifier based on the defines in sqlmon.h. If there are no locks, the text identifier is NONE, otherwise, it is any combination of the following separated by a '+' sign: ALLOW_NEW DELETE_IN_BLOCK ESCALATED INSERT NEW_REQUEST RR RR_IN_BLOCK UPDATE_DELETE WAIT_FOR_AVAIL
LOCK_CURRENT_MODE	VARCHAR(10)	lock_current_mode - Original lock mode before conversion . This interface returns a text identifier based on the defines in sqlmon.h and is one of: IN IS IX NON (if no lock) NS NW S SIX U X Z
LOCK_NAME	VARCHAR(32)	lock_name - Lock name
LOCK_RELEASE_FLAGS	BIGINT	lock_release_flags - Lock release flags .
DATA_PARTITION_ID	INTEGER	data_partition_id - Data Partition identifier . For a non-partitioned table, this element is NULL.
DBPARTITIONNUM	SMALLINT	The database partition from which the data was retrieved for this row.