Regulating backup and archive sessions

When you request a backup or archive, the client can use more than one session to the server.

The default is to use a maximum of two sessions; one to query the server and one to send file data. The client can use only one server session if you set the resourceutilization option to 1.

A client can use more than the default number of sessions when it connects to a Tivoli® Storage Manager server. For example, resourceutilization 10 permits up to eight sessions with the server. Multiple sessions can be used for querying the server and sending file data.

Multiple query sessions are used when you specify multiple file specifications with a backup or archive command. For example, if you enter the following commands and you specify resourceutilization 5, the client might start a second session to query files on file space B.

inc /Volumes/filespaceA /Volumes/filespaceB

Whether the second session starts depends on how long it takes to query the server about files that are backed up on file space A. The client might also try to read data from the file system and send it to the server on multiple sessions.

Note: During a backup operation, if you enter multiple file specifications, the result might be that files from one file specification are stored on multiple tapes and interspersed with files from different file specifications. This can decrease restore performance. Setting the collocatebyfilespec option to yes eliminates interspersing of files from different file specifications, by limiting the client to one server session per file specification. Therefore, if you store the data to tape, files for each file specification are stored together on one tape (unless another tape is required for more capacity).