15.00 - schmon -a - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
15.00
Content Type
Configuration
Publication ID
B035-1102-015K
Language
English (United States)
Last Update
2018-09-25

schmon -a

Purpose  

The schmon -a option displays or sets Allocation Group parameters.

Syntax  

 

Syntax element

Description

-a

Sets or displays Allocation Group parameters. If no additional options are specified, schmon -a displays the parameters for Allocation Groups currently in use (those with defined parameters).

AG#

An integer from 0 through 199 that identifies the Allocation Group for which parameters will be set or displayed.

  • To set parameters for a Allocation Group, follow AG# with the div and weight specifications.
  • To view information about a specific Allocation Group, follow AG# with the -s or -S options, or with no options.
  • To clear all parameters for a specific Allocation Group, follow AG# with the -x option.
  • div

    This option is obsolete, but remains for backward compatibility. div must have a value of N or S when creating or modifying an AG. (That is, div must be specified any time weight is specified.) N and S values are equivalent. The N and S values must be entered as upper case letters.

    X

    The Allocation Group is expected to process expedited work. Work requests controlled by the Allocation Group receive special treatment in the request input queue and AWT allocation phase. Requests receive superior priority in the input queue, bypassing normal requests, and are assigned to work tasks from a pool reserved for the purpose.

    You can use this option with more than one Allocation Group. When multiple Allocation Groups have the expedited attribute, work requests for all of the Allocation Groups are satisfied from a single reserved work task pool.

    Note: You can use the schmon -w command to define the reserved work pool.

    weight

    A numeric value used to compute a relative weight to determine the proportion of resources the tasks of the Allocation Group are to receive.

    Note: To use the weight option, an N or S value for div must also be used on the command line.

    limit

    A percentage limit on total CPU usage by all tasks controlled by the Allocation Group.

    The value range is from 1 through 100.

    A value of 100 indicates that no limit is to be enforced.

    If limit is not specified, no limit is enforced, and any previously defined limit for the AG is removed.

    none

    Specifies that no limit is to be enforced. This is the default value for limit. It is the same as specifying 100.

    -s

    Displays Priority Scheduler data for all sessions controlled by the specified Allocation Group on the current node.

    -S

    Displays Priority Scheduler data for all sessions controlled by the specified Allocation Group on all Teradata Database nodes.

    -T

    Displays tasks (threads) for the specified Allocation Groups on the current node (the node from which schmon was invoked). Even when used in conjunction with the -S option, -T will display only task data for the current node.

    Note: The -T option should not be used for prolonged periods of time, because it can interfere with the normal operation of Priority Scheduler.

    The -T output includes the following columns:

  • Procqueue Tsk Addr: Kernel Task Context Block address
  • Tskid: Thread ID
  • Prio: OS priority
  • Session: Task session number
  • Request: Task request number
  • Tskuse: Task CPU resource usage
  • Tskterm: Session resource usage to weight ratio
  • # Delay: Task delay count due to CPU limits
  • Delay Time: Task total delay time due to CPU limits
  • -d

    Displays the differences in data between sequential runs of schmon. Use the delay [reps] option to control timing of automatic schmon runs.

    The following symbols precede numbers that appear in the output from the -d option.

  • For decimal numbers:
  • - (a minus sign) indicates the value has decreased by the indicated amount since the previous schmon run.
  • An unsigned decimal number indicates the value has increased by the indicated amount since the previous schmon run.
  • For task data (displayed if the -T option is used with the -d option):
  • n->     indicates a task has been moved from the control of AG n to the control of the displayed AG since the previous schmon run.
  • +     indicates a task is new, started since the previous schmon run.
  • -     indicates a task that ended since the previous schmon run.
  • *     indicates a task that has changed sessions or requests since the previous schmon run.
  • For examples of the -d option output, see “schmon -m” on page 745, and “schmon -s” on page 767.

    Note: The output of the -d option shows only those items for which data has changed since the previous schmon run.

    delay [reps]

    Causes schmon -a to run again automatically after a specified delay using the current session options. delay is a positive integer that specifies the number of seconds between schmon executions.

    Use the optional reps argument, a positive integer, to specify the number of times schmon should run. If reps is not specified, schmon runs indefinitely with delay seconds between executions. In this case, schmon can be stopped by pressing Ctrl-C or otherwise killing the schmon process.

    Note: The difference between time stamps of successive information displays may not precisely match the specified delay value due to the time required for the collection activity itself.

    -x

    Clears the parameters that define the specified Allocation Group, effectively deleting it from the system (though an empty group will still appear in the output of schmon -a all).

    The Allocation Group must not be referenced by any Performance Period defined by any Performance Group.

    Usage Notes  

    A session’s tasks are assigned to Allocation Groups based on the session’s Performance Group. Each Performance Group may have from one to eight Performance Periods defined, each of which specifies an Allocation Group. As a task runs, its Performance Period changes according to limit criteria (“milestones”) that are defined along with the Performance Group. Consequently, the Allocation Group that controls a task can change over time. For more information, see “Performance Periods” on page 710.

    The following apply to MPP configurations:

  • For the -S option:
  • The count of nodes is displayed.
  • Time information is displayed.
  • If a node is offline, it is not included in the output, and the node count reflects this; however, information about this node being excluded is not displayed.
  • The following apply to SMP configurations:

  • Node count is not shown.
  • A status message that includes time of day is displayed.
  • No transient status messages are displayed.
  • Example

    To display parameters for all in-use Allocation Groups, type:

    schmon -a 

    The following appears:

                            Allocation Groups (0 - 199)
     Id Type Wght Lim Id Type Wght Lim Id Type Wght Lim Id Type Wght Lim
      1  N    5   none 2 N    10   none 3 N    20   none 4 N    40   none
     30  S   30   none 

    Example  

    The following example shows a four-node MPP system.

    To display session data for Allocation Group 1 on the current node, type:

    schmon -a 1 -s

    The following appears:

    Stats: Mon Mar  8 14:47:16 2008

                                                Session Usage       Query Usage
      AG HostID   Session   Request   #tsk  CPU(msec)  DSK(blk) CPU(msec) DSK(blk) RP PG [PP]
     === ====== ========== ========== ==== ========== ========= ========= ======== == =================
       1      0          0          0    9         60     10250        60    10250  0 L[0]

    Example  

    The following example shows a four-node system.

    Note: PDE was not up on one of the nodes.

    To display session data for Allocation Group 1 on all nodes, type:

    schmon -a 1 -S

    The following appears:

     
    Stats: 3 node(s)  Mon Mar  8 14:50:32 2008
                                                Session Usage       Query Usage
      AG HostID   Session   Request   #tsk  CPU(msec)  DSK(blk) CPU(msec) DSK(blk) RP PG [PP]
     === ====== ========== ========== ==== ========== ========= ========= ======== == =================
       1      0          0          0   19         70     20500        70    20500  0 L[0]

    Example  

    To set the expedite attribute on an Allocation Group 1, type:

    schmon -a 1 N X 30

    The following appears:

                            Allocation Groups (0 - 199)
     Id Type Weight 
      1  N      5   
    >>>>> Changed to:
      1  NX    30

    Example  

    To change the weight of Allocation Group 5 from 1 to 10, type:

    schmon -a 5 S 10 

    The following appears:

                            Allocation Groups (0 - 199)
     Id Type Weight  
      5  S      1   
    >>>>> Changed to:
      5  S     10