Different types of TSM scheduling modes - Client Polling and Server Prompted


In Tivoli Storage Manager, we can control how TSM schedules should start and who (server/client) can start the schedule initiation request.  Tivoli Storage Manager provides two different types of scheduling modes - Client-Polling and Server-Prompted

The mode indicates how client nodes interact with the server for scheduling operations. With client-polling mode, client nodes poll the server for the next scheduled event. With server-prompted mode, the server contacts the nodes at the scheduled start time.

By default, the server permits both scheduling modes. The default (ANY) allows nodes to specify either scheduling mode in their client options files. You can modify this scheduling mode.

Also Read: How TSM Server determines the eligibility of files during different types of backup ?

If you modify the default server setting to permit only one scheduling mode, all client nodes must specify the same scheduling mode in their client options file. Clients that do not have a matching scheduling mode will not process the scheduled operations. The default mode for client nodes is client-polling.

The scheduler must be started on the client node's machine before a schedule can run in either scheduling mode.

TSM Scheduling Modes

With client-polling mode, client nodes poll the server for the next scheduled event. With server-prompted mode, the server contacts the nodes at the scheduled start time.

If you modify the default so that the server permits only one scheduling mode for the server, all clients must specify the same scheduling mode in their client options file. Clients that do not have a matching scheduling mode do not process scheduled operations.

To have clients poll the server for scheduled operations - 

set schedmodes polling

Ensure that client nodes specify the same mode in their client options files.

To have the server prompt clients for scheduled operations -

set schedmodes prompted

Ensure that client nodes specify the same mode in their client options files.

To return to the default scheduling mode so that the server supports both client-polling and server-prompted scheduling modes -

set schedmodes any

Client nodes can then specify either polling or prompted mode.

Also Read: How to configure TSM Client Backup & Archive Schedules ?

Users set the scheduling mode on client nodes. They specify either the client-polling or the server-prompted scheduling mode on the command line or in the client user options file, dsm.opt & dsm.sys files. (On UNIX systems, root users set the scheduling mode in the client system options file.)

Sessioninitiation
Use the sessioninitiation option to control whether the server or client initiates sessions through a firewall. The default is that the client initiates sessions. You can use this option with the schedule command. Use this option in client option files (dsm.opt & dsm.sys files).

Syntax

                                               .-Client-----.   
>>-SESSIONINITiation-------+------------+---------------------------><
                                               '-SERVEROnly-'   

Client
Specifies that the client will initiate sessions with the server by communicating on the TCP/IP port defined with the server option tcpport. This is the default. Server prompted scheduling may be used to prompt the client to connect to the server.

SERVEROnly
Specifies that the server will not accept client requests for sessions. All sessions must be initiated by server prompted scheduling on the port defined on the client with the tcpclientport option (see Tcpclientport. Except for CAD-managed schedulers, the command line client, native GUI, and Web client GUI will still attempt to initiate sessions.

By default, clients contact the server (client-polling scheduling mode and SESSIONINITIATION= CLIENTORSERVER). 

Relation between Schedule Modes and Sessioninitiation

If SESSIONINITIATION is set to the default CLIENTORSERVER value, you can use either client-polling or server-prompted scheduling modes. The client might start sessions with the server by communicating on the TCP/IP port that was defined with a server option. Server-prompted scheduling also can be used to prompt the client to connect to the server.

Also Read: How to configure TSM Server Administrative Schedules ?

You can instead prevent clients from starting sessions, and allow only the server to start sessions with clients. To limit the start of backup-archive client sessions to the server only, do the following steps for each node:

Use the REGISTER NODE command or the UPDATE NODE command to change the value of the SESSIONINITIATION parameter to SERVERONLY, Specify the high-level address and low-level address options. These options must match what the client is using, otherwise the server will not know how to contact the client.

register node <nodename> sessioninitiation=serveronly

Set the scheduling mode to server-prompted. All sessions must be started by server-prompted scheduling on the port that was defined for the client with the REGISTER NODE or the UPDATE NODE commands. Ensure that the scheduler on the client is started. You cannot use the client acceptor (dsmcad) to start the scheduler when SESSIONINITIATION is set to SERVERONLY.




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