{}
{  The purpose of this request is to return information about the requested
{       tape unit to the caller.
{}
{       IOP$FETCH_TAPE_CAPABILITIES (SYSTEM_FILE_ID, MAXIMUM_BLOCK_LENGTH,
{             MAX_BLOCKS_PER_PHYSICAL_CALL, STATUS)
{}
{ SYSTEM_FILE_ID: (input) This parameter specifies the system
{       file identification of the file.
{}
{ MAXIMUM_BLOCK_LENGTH: (output) This parameter specifies, in bytes, the maximum
{       block length supported on the requested tape unit.
{}
{ MAX_BLOCKS_PER_PHYSICAL_CALL: (output) This parameter specifies the maximum number
{       of blocks read or written per request to the PP.
{}
{ STATUS: (output) This parameter specifies the request status.
{       Condition:
{               ioc$improper_sequence
{               ioc$improper_system_file_id
{               ioc$os_failure
{       Identifier: ioc$physical_io.
{}
