Compression

Compressing your files reduces data storage for backup versions and archive copies of your files. It can, however, affect Tivoli® Storage Manager throughput. A fast processor on a slow network connection benefits from compression, but a slow processor on a fast network connection does not.

Use the compression option with the archive, incremental, and selective commands.

The backup image command uses the compression option value specified in the dsm.sys file. This option is valid on the initial command line and in interactive mode. The server can also define this option which overrides the client value.

The backup image command uses the compression option value specified in the dsm.opt file. This option is valid on the initial command line and in interactive mode. The server can also define this option which overrides the client value.

Tivoli Storage Manager backs up a sparse file as a regular file if client compression is off. Set compression yes to enable file compression when backing up sparse files to minimize network transaction time and maximize server storage space.

If you set compressalways yes, compression continues even if the file size increases. To stop compression if the file size grows, and resend the file uncompressed, set compressalways no.

If you set compression yes, you can control compression processing in the following ways:

• Use the exclude.compression option in your client options file (dsm.opt) to exclude specific files or groups of files from compression processing.
• Use the exclude.compression option in your client system-options file (dsm.sys) to exclude specific files or groups of files from compression processing.
• Use the include.compression option in your client options file (dsm.opt) to include files within a broad group of excluded files for compression processing.
• Use the include.compression option in your client system-options file (dsm.sys) to include files within a broad group of excluded files for compression processing.

This option controls compression only if your administrator specifies that your client node can compress files before sending them to the server.

Supported Clients

This option is valid for all clients. The server can also define this option.

Options File

Place this option in the dsm.sys file within a server stanza. You can set this option on the Backup tab, Compress objects check box of the Preferences editor.

Place this option in the client options file (dsm.opt). You can set this option on the Backup tab, Compress objects check box of the Preferences editor.

                .-No--.   
>>-COMPRESSIon--+-----+----------------------------------------><
                '-Yes-'   

Parameters

No

Files are not compressed before they are sent to the server. This is the default.

Yes

Files are compressed before they are sent to the server.