Fujitsu MAT3300FC 用户手册

C141-C008 

3-5 

 

1)  If the amount of transfer data specified in a command is 

smaller than the capacity of the cache segment, all the data 
necessary for execution of the command are pre-fetched in a 
batch in the processing in 1) above, so the value specified in 
the buffer empty ratio has not meaning. 

2)  If the amount of data processed with a single command exceeds 

the capacity of one cache segment, in order to avoid frequent 
repetition of Loop OPEN/CLOSE processing during command 
execution, and in order to escape the occurrence of data 
underrun, it is necessary to set the buffer empty ratio (see 
Section 3.1.2) of the MODE SELECT parameter so the 
difference in the data transfer rates between the INIT (FC 
interface) and the disk drive is maintained in a good balance. 

Figure 3.3 shows an example of the data buffer operating state during a write 
operation.  Details are explained in section 3.1.2. 

 

(1)  MODE SELECT parameter 

In order to make it possible to control from the INIT the Loop OPEN processing 
start timing for executing data transfers to the FC interface in read and write 
operations, the IDD is provided with the MODE SELECT parameter 
(Disconnect/Reconnect Parameter: Page code = 2) shown in Table3.1.  The user can 
set the optimum operating state in the system environment as necessary.  See 
Section 4.1.4 for details of the MODE SELECT command.