Data transfer method (Framed Message Transfer Type)
HULFT Ver.7 or higher allows you to select either the Transfer Speed Priority mode or the Error Detection Priority mode as the data transfer method. In Transfer Speed Priority mode, HULFT transfers data without waiting for the receiving result notification from remote hosts.
Using the Transfer Speed Priority mode improves transfer speed in high-speed network environments and during large data transfer. The Error Detection Priority mode, which is the conventional transfer method of HULFT Ver.6 or lower, waits for the receiving result notification from the remote host and then proceeds to the next data for transfer. Therefore, the transfer speed in Error Detection Priority mode is slower than in Transfer Speed Priority mode, but is faster in detection of errors.
Depending on your network environment, the transfer speed in Transfer Speed Priority mode might be slower than in Error Detection Priority mode.
Transfer Speed Priority Mode and Error Detection Priority Mode
Shown below is an illustration of the difference between the Transfer Speed Priority mode and the Error Detection Priority mode.
Figure 2.22 Difference between Transfer Speed Priority Mode and Error Detection Priority Mode
To specify a data transfer method, both the host on the sending side and the host on the receiving side need to use HULFT Ver.7 or higher. In addition, if these hosts use HULFT-HUB, HUB-Server on the host to be routed through should be Ver.2.2 or higher. If you use a lower version of HULFT, data transfer is carried out in Error Detection Priority mode.
Further, to use the Transfer Speed Priority mode, both the host on the sending side and the host on the receiving side must be set to operate in Transfer Speed Priority mode. If either host has specified 'N' (Error Detection Priority Mode), HULFT transfers data in Error Detection Priority mode.
Specification of Framed Message Transfer Type
You can specify a data transfer method by selecting one of the options for the Framed Message Transfer Type (PROCTRANSTYPE) of the System Environment Settings. There are four options for the Framed Message Transfer Type:
- N (Error Detection Priority Mode)
-
Transfer data in Error Detection Priority mode for both the Send processing and the Receive processing.
- S (Send Speed Priority Mode)
-
For the Send processing, transfer data in Transfer Speed Priority mode. For the Receive processing, transfer data in Error Detection Priority mode.
- R (Receive Speed Priority Mode)
-
For the Receive processing, transfer data in Transfer Speed Priority mode. For the Send processing, transfer data in Error Detection Priority mode.
- A (Send and Receive Speed Priority Mode)
-
Transfer data in Transfer Speed Priority mode for both the Send processing and the Receive processing.
The combination of settings for Framed Message Transfer Type on the sending-side host and receiving-side host determines which data transfer method is used. See the following table:
|
Sending Host |
Receiving Host |
|||
|---|---|---|---|---|
|
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) |
|
|
✓ |
✓ |
|
✓ |
: |
HULFT operates in Transfer Speed Priority mode. |
|
Blank |
: |
HULFT operates in Error Detection Priority mode. |
Specify the Framed Message Transfer Type according to the user's circumstances for sending and receiving. Shown below is an illustration of specification examples of the Framed Message Transfer Type based upon the user's circumstances:
Figure 2.23 Specification Examples of Framed Message Transfer Types
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 the Error Detection Priority mode and the Transfer Speed Priority mode.
Examples when an error occurs on the host on the sending side
Figure 2.24 Error Detection Timing in Transfer Speed Priority Mode and Error Detection Priority Mode (Sending Host)
Examples when an error occurs on the host on the receiving side
Figure 2.25 Error Detection Timing in Transfer Speed Priority Mode and Error Detection Priority Mode (Receiving Host)
In Transfer Speed Priority mode, the usage of resources during the Send processing and the Receive processing is greater than in Error Detection Priority mode. Higher usage may cause a delay in error detection for transfer and in acknowledgment of cancelation.
Points to Be Noted
If there is no improvement in transfer speed despite the specification of the Transfer Speed Priority mode, the following factors may be affecting the speed. Refer to the following information to solve the problem:
Framed Message Transfer Type setting on remote host
If the Framed Message Transfer Type is specified as 'N' (Error Detection Priority Mode) on the remote host, change the setting for the Framed Message Transfer Type so that HULFT operates in Transfer Speed Priority mode. For combinations of the Framed Message Transfer Type settings that enable the Transfer Speed Priority mode, refer to Table 2.7 Combination of Framed Message Transfer Types.
Version of HULFT product on remote host
If the remote host uses a version of HULFT products that does not support the Transfer Speed Priority mode, upgrade HULFT to a product version that supports the Transfer Speed Priority mode for both hosts on the sending side and the receiving side.
Insufficient network bandwidth
The Transfer Speed Priority mode requires a greater network traffic capacity than the Error Detection Priority mode. Insufficient network bandwidth reduces the effect of the Transfer Speed Priority mode.
Socket Buffer Size for Data Sending (SNDSOCKSIZE) and Socket Buffer Size for Data Receiving (RCVSOCKSIZE) settings on sending host and receiving host
Modify the Socket Buffer Size for Data Sending and the Socket Buffer Size for Data Receiving in the System Environment Settings on HULFT. Usually, the larger the Socket Buffer Size for Data Sending and the Socket Buffer Size for Data Receiving are, the faster the transfer speed becomes, but optimum values vary depending on your network environment.
Transfer unit on sending host
Modify the Transfer Block Length (BLOCKLEN) and the Transfer Block Count (BLOCKNUM) in the Send Management Information of HULFT to optimum values for your network. Usually, the greater the size of the transfer unit (Transfer Block Length x Transfer Block Count), the faster the transfer speed becomes, but optimum values vary depending on your network environment.