Command-based communications between an initiator and a target

A communication control method between an initiator and a target, wherein the initiator has a storage area, comprising:

• the initiator issuing a predetermined command including a data address in the storage area to the target and holding the command;
• and
• the target holding the command from the initiator in a queue, reading out or writing data from or to the storage area of the initiator in accordance with the data address included in the command from the initiator, and issuing a completion message to the initiator,
• wherein the initiator re-issuably holds the issued command until the initiator receives the completion message indicating completion of processing corresponding to the command from the target.

A communication system comprising an initiator and a target, wherein said initiator has a storage area,

• wherein the initiator includes means for issuing a predetermined command including an identifier to the target and holding the command;
• wherein the target includes means for reading out or writing data from or to the storage area of the initiator in response to the command from the initiator, and for issuing a completion message to the initiator,
• wherein the initiator re-issuably holds the issued command until the initiator receives the completion message indicating completion of processing corresponding to the command from the target, and
• wherein when a connection between the initiator and target is temporarily disconnected and is connected again, the target compares an identifier of the command issued by the initiator with a held identifier, and the target makes a read or write from a held offset of the storage area when the two identifiers match, and issues a process completion message corresponding to the command to the initiator without making a read or write to the storage area of the initiator when the two identifiers do not match.

A computer readable storage medium for exchanging data in response to issuance of a command which includes a data address, wherein a target holds the command in a queue and reads out or writes data in accordance with the data address included in the command, said code comprising:

• code to re-issuably hold the command issued to the target until a process completion message indicating completion of processing corresponding to the command is received from the target;
• code to hold a correspondence between the command issued to the target, and a storage area from or to which data is read out or written by the target in accordance with the data address in the command;
• and
• code to re-issue the re-issuably held command to the target when a connection with the target is temporarily disconnected and connected again.