HP Raining DataCorp. mvEnterprise manual Special Considerations for 4mm DAT Units

5.Select these options as indicated the following screen:

￿￿BLOCK SIZE (0=variable length). Type 0.

￿￿Use DEVICE BUFFERS during writes. Type yes.

￿￿Use data COMPRESSION. See the “Special Considerations for 4mm DAT Units” section following for information on selecting the compression option.

2.2.1 Special Considerations for 4mm DAT Units

For 4mm DAT drives, compression needs to be correctly specified. Newer devices support data compression, allowing them to write between 2-3 times the normal quantity of data on the tape, while at the same time reducing the time taken to read and write tapes. Normally, this feature should be turned on. However, if you are writing tapes to be read by other 4mm DAT units that cannot handle compressed data, you need to turn data compression off.

2.2.2 Special Considerations for Quarter-Inch Cartridge Tape Units

Tape density and block size are of particular importance when using quarter-inch tape units. Density setting 34 selects QIC 2.5GB mode of operation (COMPRESSION = NO), further selecting COMPRESSION = YES in this mode selects QIC 5.0GB mode, 21 selects QIC1000 mode, 17 selects QIC525 mode, 16 selects QIC150 mode, and 15 selects QIC120 mode.

In all cases you must set the tape BLOCK size to 512.

Depending upon the model of the tape drive installed in your system and the specification of the tape cartridge used, some of the above settings may not be applicable or allowable. Tape units automatically read tapes created at any of the applicable densities, and write them at either of the

mvEnterprise Release 4.1 on AIX Installation Guide Page 45