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Administrator's Guide


Managing Tivoli Storage Manager Sessions

Each time an administrator or client node connects with the server, an administrative or client session is established. Tivoli Storage Manager tracks its sessions in the server database. Backup-archive clients are eligible for client restartable restore sessions, however, application clients are not. See Managing Client Restartable Restore Sessions for more information.

Administrators can perform the following activities when managing Tivoli Storage Manager sessions:

Task Required Privilege Class
Displaying information about client sessions Any administrator
Canceling a client session System or operator
Disabling or enabling a client session System or operator
Freeing links for client connections Administrator with root authority

Displaying Information about Tivoli Storage Manager Sessions

Each client session is assigned a unique session number. To display information about client sessions, enter:

query session

Figure 41 shows a sample client session report.

Figure 41. Information about Client Sessions

+--------------------------------------------------------------------------------+
|  Sess Comm.  Sess     Wait   Bytes   Bytes Sess  Platform Client Name          |
|Number Method State    Time    Sent   Recvd Type                                |
|------ ------ ------ ------ ------- ------- ----- -------- -----------          |
|   471 Tcp/Ip IdleW   36 S      592     186 Node  WinNT    JOEUSER              |
|   472 Tcp/Ip RecvW    0 S      730 838.2 K Node  WinNT    STATION1             |
|   475 HTTP   Run      0 S        0       0 Admin WebBrow- ADMIN                |
|                                                  ser                           |
|                                                                                |
+--------------------------------------------------------------------------------+

You can determine the state of the server by examining the session state and wait time to determine how long (in seconds, minutes, or hours) the session has been in the current state.

Server Session States

The server session state can be one of the following:

Start
Connecting with a client session.

Run
Executing a client request.

End
Ending a client session.

RecvW
Waiting to receive an expected message from the client while a database transaction is in progress. A session in this state is subject to the COMMTIMEOUT limit.

SendW
Waiting for acknowledgment that the client has received a message sent by the server.

MediaW
Waiting for removable media to become available.

Aggregation can cause multiple media waits within a transaction and is indicated by one client message. For more information, see Reclaiming Space in Sequential Access Storage Pools.

Note:
If QUERY SESSION FORMAT=DETAILED is specified, the Media Access Status field displays the type of media wait state.

IdleW
Waiting for communication from the client, and a database transaction is NOT in progress. A session in this state is subject to the IDLETIMEOUT limit as specified in the server options file.

If a client does not initiate communication within the specified time limit set by the IDLETIMEOUT option in the server options file, then the server cancels the client session.

For example, if the IDLETIMEOUT option is set to 30 minutes, and a user does not initiate any operations within those 30 minutes, then the server cancels the client session. The client session is automatically reconnected to the server when it starts to send data again.

Canceling a Tivoli Storage Manager Session

You can cancel a client session with the CANCEL SESSION command and the associated session number. Canceling sessions may be necessary when a user's machine is not responding or as a prerequisite to halting the server. Administrators can display a session number with the QUERY SESSION command as described in Displaying Information about Tivoli Storage Manager Sessions.

Users and administrators whose sessions have been canceled must reissue their last command to access the server again.

If an operation, such as a backup or an archive process, is interrupted when you cancel the session, the server rolls back the results of the current transaction. That is, any changes made by the operation that are not yet committed to the database are undone. If necessary, the cancellation process may be delayed.

If the session is in the Run state when it is canceled, the cancel process does not take place until the session enters the SendW, RecvW, or IdleW state. For details, see Server Session States.

If the session you cancel is currently waiting for a media mount, the mount request is automatically canceled. If a volume associated with the client session is currently being mounted by an automated library, the cancel may not take effect until the mount is complete.

For example, to cancel a session for client MARIE:

  1. Query client sessions to determine the session number as shown Figure 41. The example report displays MARIE's session number 6.
  2. Cancel node MARIE's session by entering:
    cancel session 6
    

If you want to cancel all backup and archive sessions, enter:

cancel session all

When a Client Session is Automatically Canceled

Client sessions can be automatically canceled based on the settings of the following server options:

COMMTIMEOUT
Specifies how many seconds the server waits for an expected client message during a transaction that causes a database update. If the length of time exceeds this time-out, the server rolls back the transaction that was in progress and ends the client session. The amount of time it takes for a client to respond depends on the speed and processor load for the client and the network load.

IDLETIMEOUT
Specifies how many minutes the server waits for a client to initiate communication. If the client does not initiate communication with the server within the time specified, the server ends the client session. For example, the server prompts the client for a scheduled backup operation but the client node is not started. Another example can be that the client program is idle while waiting for the user to choose an action to perform (for example, backup archive, restore, or retrieve files). If a user starts the client session and does not choose an action to perform, the session will time out. The client program automatically reconnects to the server when the user chooses an action that requires server processing. A large number of idle sessions can inadvertently prevent other users from connecting to the server.

THROUGHPUTDATATHRESHOLD
Specifies a throughput threshold, in kilobytes per second, a client session must achieve to prevent being cancelled after the time threshold is reached. Throughput is computed by adding send and receive byte counts and dividing by the length of the session. The length does not include time spent waiting for media mounts and starts at the time a client sends data to the server for storage. This option is used in conjunction with the THROUGHPUTTIMETHRESHOLD server option.

THROUGHPUTTIMETHRESHOLD
Specifies the time threshold, in minutes, for a session after which it may be canceled for low throughput. The server ends a client session when it has been active for more minutes than specified and the data transfer rate is less than the amount specified in the THROUGHPUTDATATHRESHOLD server option.

Refer to the Administrator's Reference for more information.

Disabling or Enabling Access to the Server


Task Required Privilege Class
Disabling and enabling client node access to the server System or operator
Displaying server status Any administrator

You can prevent clients from establishing sessions with the server by using the DISABLE SESSIONS command. This command does not cancel sessions currently in progress or system processes such as migration and reclamation. For example, to disable client node access to the server, enter:

disable sessions

You continue to access the server and current client activities complete unless a user logs off or an administrator cancels a client session. After the client sessions have been disabled, you can enable client sessions and resume normal operations by entering:

enable sessions
 

You can issue the QUERY STATUS command to determine if the server is enabled or disabled.

Managing Client Restartable Restore Sessions

Some large restore operations may invoke a special type of restore operation called client restartable restore sessions. These special sessions allow users to restart the restore session from where it left off if the session was interrupted. Tivoli Storage Manager identifies client restartable restore sessions by displaying message ANS1247I on the client machine when the sessions start. These restore sessions can be restarted as long as the restore interval has not expired.

When a restartable restore session is saved in the server database the file space is locked in server storage. The following is in effect during the file space lock:

The RESTOREINTERVAL server option allows administrators to specify how long client restartable restore sessions are saved in the server database. Consider scheduled backup operations when setting this option. For more information, refer to the RESTOREINTERVAL server option in Administrator's Reference..

Administrators can perform the following activities when managing client restartable restore sessions:

Task Required Privilege Class
Displaying information about client restartable restore sessions Any administrator
Canceling client restartable restore sessions System or operator
Interrupting client restartable restore sessions System or operator

Displaying Information about a Client Restartable Restore Session

You can display information about client restartable restore sessions with the QUERY RESTORE command. For example, to determine which client nodes have eligible restartable restore sessions, enter:

query restore

Restartable restore sessions have a negative session number.

Canceling a Client Restartable Restore Session

When a client restore session is in a restartable state, the file space is locked in server storage and no files can be moved from sequential volumes. This prevents the data from being migrated, moved, reclaimed, or backed up by another operation. These sessions will automatically expire when the specified restore interval has passed.

An administrator can cancel a restartable restore session that is in an active or restartable state. If the restore session is active, any outstanding mount requests related to the active session are automatically canceled. When a restartable restore session is canceled with the CANCEL RESTORE command, it cannot be restarted from the point of interruption. A restartable restore session always has a negative session number.

To cancel a restartable restore session, you must specify the session number. For example:

cancel restore -1

Interrupting an Active Client Restartable Restore Session

An administrator can interrupt an active restartable restore session and have the option to later restart the session from its point of interruption by canceling the session.

cancel session -2


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