For UNIX platforms that cannot reliably detect the end-of-tape marker, you must indicate how many kilobytes can be dumped to a tape.
If you specify the physical path name of the dump device, include the capacity = number_kilobytes parameter in the dump command. If you specify the logical dump device name, the Backup Server uses the size parameter stored in the sysdevices table, unless you override it with the capacity = number_kilobytes parameter.
The specified capacity must be at least 5 database pages (each page requires 2048 bytes). SAP recommends that you specify a capacity that is slightly below the capacity rated for your device.
A general rule for calculating capacity is to use 70 percent of the manufacturer’s maximum capacity for the device, and allow 30 percent for overhead (inter-record gaps, tape marks, and so on). This rule works in most cases, but may not work in all cases because of differences in overhead across vendors and devices.