Data Transfer method (Framed Message Transfer)
HULFT Ver.7 or higher allows you to select 'Transfer Speed Priority mode' or 'Error Detection Priority mode.' In Transfer Speed Priority mode, HULFT transfers data without waiting for the receiving result notification from the remote host.
Using Transfer Speed Priority mode improves the transfer speed in high-speed network environments and for large data transfers. Error Detection Priority mode, which is the conventional transfer method for versions of HULFT lower than Ver.7, waits for the confirmation of block transfer from the remote host and then proceeds to the transfer of the next block. Therefore, the transfer speed in Error Detection Priority mode is slower than in Transfer Speed Priority mode, yet the former performs error detection more swiftly.
Depending on your network environment, the transfer speed might be slower for Transfer Speed Priority mode than for Error Detection Priority mode.
(1) Transfer Speed Priority Mode and Error Detection Priority Mode
Shown below is an illustration of the difference between Transfer Speed Priority mode and Error Detection Priority mode.
Figure 2.22 Difference between Transfer Speed Priority Mode and Error Detection Priority Mode
To set the data transfer method, both the sending host and receiving host should use HULFT Ver.7 or higher. In addition, the HUB-Server to be routed through should be Ver.2.2 or higher, if these hosts use HULFT-HUB. If you use a lower version of HULFT (namely, HULFT Ver.6 or lower), data transfer is performed in Error Detection Priority mode.
Further, the use of Transfer Speed Priority mode requires both hosts on the sending side and the receiving side to be set to Transfer Speed Priority mode. If either host is set to Error Detection Priority mode, HULFT transfers data in Error Detection Priority mode.
(2) Setting of Framed Message Transfer Type
You can set the data transfer method with Framed Message Transfer Type (proctranstype) in the System Environment Settings. There are four options for Framed Message Transfer Type:
- N (Error Detection Priority Mode)
-
This option transfers data in Error Detection Priority mode, for both sending and receiving.
- S (Send Speed Priority Mode)
-
This option transfers data in Transfer Speed Priority mode for sending, and in Error Detection Priority mode for receiving.
- R (Receive Speed Priority Mode)
-
This option transfers data in Transfer Speed Priority mode for receiving, and in Error Detection Priority mode for sending.
- A (Send and Receive Speed Priority Mode)
-
This option transfers data in Transfer Speed Priority mode for both sending and receiving.
The combination of Framed Message Transfer types for the sending side and the receiving side determines which data transfer method will be performed. See the following table:
|
Sending Side |
Receiving Side |
||||
|---|---|---|---|---|---|
|
N |
S |
R |
A |
||
|
N (Error Detection Priority Mode) |
|
|
|
|
|
|
S (Send Speed Priority Mode) |
|
|
✓ |
✓ |
|
|
R (Receive Speed Priority Mode) |
|
|
|
|
|
|
A (Send and Receive Speed Priority Mode) |
|
|
✓ |
✓ |
|
|
✓ |
: |
Operation in Transfer Speed Priority mode |
|
Blank |
: |
Operation in Error Detection Priority mode |
Framed Message Transfer Type should be set based upon the user's sending and receiving conditions. The following illustration shows setting examples for the Framed Message Type based upon the user's sending and receiving conditions.
Figure 2.23 Setting Examples for Framed Message Transfer Types
(3) Timing of error detection
The timing of error detection differs depending on the specified data transfer method. This section explains the difference in the timing of error detection between Error Detection Priority mode and Transfer Speed Priority mode.
Examples when an error occurs at the host on the sending side
Figure 2.24 Error Detection Timing in Transfer Speed Priority Mode and Error Detection Priority Mode (Host on Sending Side)
Examples when an error occurs at the host on the receiving side
Figure 2.25 Error Detection Timing in Transfer Speed Priority Mode and Error Detection Priority Mode (Host on Receiving Side)
In Transfer Speed Priority mode, the utilization of resources varies more widely than in Error Detection Priority mode, which may cause a delay in the error detection timing of the transfer and the acknowledgment timing of cancelation.
(4) Points to be noted
If there is no improvement in transfer speed when Transfer Speed Priority mode is set, consider the following factors. Solve your problem by considering the following information:
The partner host specifies Error Detection Priority mode
Set Framed Message Transfer Type to any one of Transfer Speed Priority mode options both for sending and receiving hosts.
The partner host uses a version of HULFT that does not support Transfer Speed Priority mode
Upgrade HULFT to the product version that supports Transfer Speed Priority mode both for sending and receiving hosts.
Network bandwidth is insufficient
Transfer Speed Priority mode generates more network traffic than Error Detection Priority mode. Insufficient network bandwidth reduces the effectiveness of Transfer Speed Priority mode.
The Socket Buffer Size for Data Sending on sending and/or receiving hosts is too small
Modify the setting of Socket Buffer Size for Data Sending (sndsocksize) in the System Environment Settings on HULFT. Usually, the greater Socket Buffer Size for Data Sending is, the faster the transfer speed becomes, yet the optimum value varies depending on the network environment.
The transfer block size on the sending side does not have the optimum value for the network
Modify the setting of Transfer Block Size in the Send Management Information on HULFT. Usually, the greater the Transfer Block Size is, the faster the transfer speed becomes, yet the optimum value varies depending on the network environment.