How Randomization option randomize TSM client schedules within a startup window


IBM Spectrum Protect formerly known as Tivoli Storage Manager (TSM) has a special feature called RANDOMIZATION, which can be used to reduce the number of requests from a client within a backup window, which eventually decrease the load and increases the performance of TSM Server. Each schedule has a window during which schedule execution can begin. To balance network and server load, the start times for clients can be scattered across that window.  Use this command to specify the fraction of the window over which start times for clients are distributed.

Randomization is the TSM Server option parameter which is used to set randomized start times within the startup window of each schedule for clients by using the client-polling scheduling mode. A startup window is the start time and duration during which a schedule must be initiated. A client-polling scheduling mode is a client/server communication technique where the client queries the server for work.

How Randomization works in TSM Server ?

The randomization occurs at the beginning of the window to allow time for retries, if necessary. Randomization does not occur if the client's first contact with the server is after the start time for the event. You can issue the QUERY STATUS command to display the value for the schedule randomization percentage. At installation, the default value is 25 percent.
Set the randomization percentage to a value greater than 0 to prevent communication errors. Communication errors can result from a large group of clients contacting the server simultaneously. If you do experience communication errors, you can increase the randomization percentage so that client contact is spread out. This decreases the chance for communication overload and failure.

Syntax

>>-Set RANDomize--percent--------------------------------------><

Parameters
percent (Required)

Specifies the percentage of the startup window over which the start times for individual clients are distributed. You can specify an integer from 0 to 50. A value of 0 indicates that no randomization occurs and that all clients execute schedules at the beginning of the startup windows.

Also Read: Different types of Incremental Backups

A value of 50 indicates that clients are assigned start times that are randomly scattered across the first half of each startup window. At installation, this value is 25, indicating that the first 25 percent of the window is used for randomization. If you have specified DURUNITS=INDEFINITE in the DEFINE SCHEDULE command, the percentage is applied to a 24 hour period. For example, a value of 25 percent would result in a 6 hour window.

Ex: Set randomization to 50 percent

                                         set randomize 50




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