compress 

• no : No file compression.
• yes : Software compression of files during backup.
• hardware : Should be set when tape units that support hardware compression are used. BRRESTORE handles this setting as compress = no . Just setting this parameter does not activate hardware compression. It is merely information for BRBACKUP/BRARCHIVE. You also have to configure your backup device accordingly. This value is also supported for backups on disk with hardware-compressing file systems on Windows NT and AIX operating systems.
• only : Software compression, but no backup of files is started. This setting is not used by BRRESTORE.

If you use tape units that support hardware compression, SAP recommends that you perform software compression of the entire database with parameter compress = only at least once a month, so that the current compression rate can be determined for each of the data files. When you use this parameter, backup is not started.

If you do not want to compress the entire database, you should at least compress those database files where a lot of changes take place. To determine these files, compare the compression rates of all files in two subsequent compression operations. The compression rates for files that have not changed will probably remain constant in the future, as well.

After extreme database changes (reorganization, release upgrade, transfer of large quantities of data), you should always start the software compression in order to determine the compression rates for the entire database.

The setting of parameter backup_dev_type is not relevant for this activity, since no backup is started.

Check the setting of option -b 12 in command compress_cmd.