Bi-directional data transfer within a single i/o operation

ES 2 359 614 T3

DESCRIPTION

FIELD OF THE INVENTION

This discussion refers generally to input / output (I / O) processing, and in particular, to the provision of an I / O operation that includes both input and output data.

BACKGROUND OF THE INVENTION

Input / output (I / O) operations are used to transfer data between memory and I / O devices in an I / O processing system. Specifically, data is written from memory to one or more I / O devices, and data is read from one or more I / O devices to memory by executing I / O operations.

To facilitate the processing of I / O operations, an I / O subsystem of the I / O processing system is used. The I / O subsystem is coupled to main memory and I / O devices in the I / O processing system, and directs the flow of information between memory and I / O devices. An example of an I / O subsystem is a channel subsystem. The channel subsystem uses channel paths as the means of communication. Each channel path includes a channel coupled to a control unit, the control unit further being coupled to one or more I / O devices.

The channel subsystem can use channel command words (CCWs) to transfer data between I / O and memory devices. A CCW specifies the order to execute. For commands that initiate certain I / O operations, the CCW designates the memory area associated with the operation, the action to take each time a transfer to or from the area is completed, and other options.

During I / O processing, a channel retrieves a list of CCWs from memory. The channel parses each order in the list of CCWs and forwards a series of the orders, each order in its own entity, to a control unit coupled to the channel. The control unit then processes the orders. The channel keeps track of the status of each order and controls when the next set of orders will be sent to the control unit for processing. The channel guarantees that each order is sent to the control unit in its own entity. In addition, the channel deduces certain information associated with the processing of the response of the control unit for each command.

Running I / O processing on the basis of each CCW can involve a great deal of processing work for the channel subsystem, as the channels parse CCWs, track status information, and react to feedback responses. control units. Therefore, it may be beneficial to shift much of the processing load associated with interpreting and managing CCW and status information from the channel subsystem to the control units. Simplifying the role of channels in communication between control units and an operating system in the I / O processing system can increase communication throughput as less agreement signaling is executed. Simplifying the role of channels in communication can include grouping multiple commands into a single I / O operation. However, modifying command sequences by grouping two or more commands together in a single I / O operation can result in the I / O operation presenting both input data and output data. Currently, an I / O operation can support a single data area that can be used for data input or data output, but not both in the same I / O operation. This limits the types of orders that can be grouped together in a single I / O operation and therefore limits the increase in throughput that can be achieved by grouping orders. Accordingly, there is a need in the art to be able to transfer both input data and output data within a single I / O operation.

US 6,230,218 discloses the simplification of an I / O processing for an I / O operation in a host computer system.

BRIEF SUMMARY OF THE INVENTION

The invention provides a method as claimed in claim 1 and a corresponding computer system and program.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is considered as the present invention is particularly indicated and clearly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts an embodiment of an I / O processing system that incorporates and uses one or more aspects of the present invention;

FIG. 2A depicts an example of a prior art channel command word;

ES 2 359 614 T3 FIG. 2B represents a channel program with prior art channel command words;

FIG. 3 depicts an embodiment of a prior art handshake used in communication between a channel and a control unit to execute the channel program with channel command words of FIG. 2B;

FIG. 4 depicts an embodiment of a channel program with transport control words (TCW), according to one aspect of the present invention;

FIG. 5 depicts an embodiment of a handshake used to communicate between a channel and a control unit in order to execute the TCW channel program of FIG. 4, according to one aspect of the present invention;

FIG. 6 depicts an embodiment of a prior art handshake used to communicate between a channel and a control unit in order to execute four read commands of a channel program of channel command words;

FIG. 7 depicts an embodiment of a handshake used to communicate between a channel and a control unit in order to process the four read commands of a TCW channel program, according to one aspect of the present invention;

FIG. 8 depicts an embodiment of a control unit and channel subsystem, according to one aspect of the present invention;

FIG. 9 depicts an embodiment of a TCW according to one aspect of the present invention;

FIG. 10 depicts an embodiment of a TCW channel program, according to one aspect of the present invention;

FIG. 11 depicts an embodiment of a handshake protocol used to communicate between a channel and a control unit in order to execute the TCW channel program of FIG. 10, according to one aspect of the present invention;

FIG. 12 depicts an embodiment of a process for bidirectional transfer of data in a single I / O operation, in accordance with one aspect of the present invention; and FIG. 13 depicts an embodiment of an article of manufacture incorporating one or more aspects of the present invention.

The description explains the preferred embodiments of the invention, together with advantages and features, by way of example, with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with one aspect of the present invention, input / output (I / O) processing is simplified by allowing a single I / O operation to include both input data and output data. In this way, each I / O operation can be used to transfer both a continuous input stream and a continuous output stream. This simplifies I / O processing by reducing communications between components of an I / O processing system used to perform I / O processing. For example, the number of exchanges and sequences between an I / O communication adapter, such as a channel, and a control unit is reduced. This is achieved by sending a plurality of commands from the I / O communication adapter to the control unit, as a single entity to be executed by the control unit, and by sending, by the control unit, the data resulting from the orders, if any, in the form of a single entity. The plurality of device command words (DCWs) sent as a single entity to a control unit can include both read and write commands.

The plurality of commands are included in one block, referred to herein as a transport command control block (TCCB), one of the addresses of which is specified in a transport control word (TCW). The TCW is sent from an operating system (OS) or other application to the I / O communications adapter, which in turn forwards the TCCB in a command message to the control unit for processing. The control unit processes each of the commands in the absence of status monitoring for said individual commands by the I / O communication adapter. The plurality of commands is also referred to as a channel program, which is parsed and executed in the control unit rather than the I / O communication adapter.

In an exemplary embodiment, the TCW provides the channel pointers for all the control blocks required to execute the I / O operation. In an exemplary embodiment, the TCW includes pointers to both an input data address and an output data address. This allows data transfer in both directions (for example, from a channel to a control unit and from a control unit to a channel) in

ES 2 359 614 T3 a single I / O operation.

It is described, with reference to FIG. 1, an example of an I / O processing system incorporating and using one or more aspects of the present invention. The I / O processing system 100 includes a host system 101, which further includes, for example, a main memory 102, one or more central processing units (CPUs) 104, a storage control element 106, and a subsystem 108 channels. The host system 101 may be a large-scale computer system, such as a mainframe type host computer or a server. The I / O processing system 100 also includes one or more control units 110 and one or more I / O devices 112, each of which is described later.

Main memory 102 stores data and programs, which can be input from I / O devices 112. For example, main memory 102 may include one or more operating systems (OSs) 103 that are run by one or more of the CPUs 104. For example, a CPU 104 may run a Linux® operating system 103 and a z / operating system. OS® 103 as different instances of a virtual machine. Main memory 102 is directly addressable and provides high speed data processing by CPUs 104 and channel subsystem 108.

CPU 104 is the control center for I / O processing system 100. It contains sequencing and processing mechanisms for the execution of instructions, interrupt actions, timing functions, initial loading of programs, and other functions associated with machines. CPU 104 is coupled to storage control element 106 through a connection 114, such as a bidirectional or unidirectional bus.

Storage control element 106 is coupled to main memory 102 through a connection 116, such as a bus; to CPUs 104 through connection 114; and to the channel subsystem 108 through a connection 118. The storage control element 106 controls, for example, queuing and the execution of requests made by one or more of the CPU 104 and the channel subsystem 108 .

In an exemplary embodiment, channel subsystem 108 provides a communications interface between host system 101 and control units 110. Channel subsystem 108 is coupled to storage control element 106, as described above, and to each of control units 110 through a connection 120, such as a serial link. Connection 120 can be implemented in any manner known in the art, including an optical link, that uses single or multimode waveguides in a Fiber Channel (Fiber Channel) fabric (eg, a Fiber Channel network). Channel subsystem 108 directs the flow of information between I / O devices 112 and main memory 102. It exempts CPUs 104 from the task of communicating directly with I / O devices 112 and allows data processing to proceed at the same time as I / O processing. Channel subsystem 108 uses one or more channel paths 122 as communication links in managing the flow of information to or from I / O devices 112. As part of the I / O processing, the channel subsystem 108 also performs the path management functions to perform tests regarding the availability of channel paths, select an available channel path 122, and initiate execution of the operation. with I / O devices 112.

Each channel path 122 includes a channel 124 (in one example, as shown in FIG. 1, channels 124 are located within channel subsystem 108), one or more control units 110, and one or more connections 120 In another example, it is also possible to have one or more dynamic switches (not shown) as part of channel path 122. A dynamic switch can be coupled to a channel 124 and a control unit 110 and provides the ability to physically interconnect any two links that are hooked to the switch. In another example, it is also possible to have multiple systems, and therefore multiple channel subsystems (not shown) hooked up to one or more of the control units 110.

Also located in channel subsystem 108 are subchannels (not shown). A subchannel is provided for each I / O device 112 accessible for a program through the channel subsystem 108, and said subchannel is dedicated to each mentioned device. A subchannel (for example, a data structure, such as a table) provides the logical aspect of a device for the program. Each subchannel provides information regarding the associated I / O device 112 and its attachment to the channel subsystem 108. The subchannel also provides information regarding I / O operations and other functions involving the associated I / O device 112. The subchannel is the means by which the subchannel subsystem 108 provides information about associated I / O devices 112, to the CPUs 104, which obtain this information by executing I / O instructions.

Channel subsystem 108 is coupled to one or more control units 110. Each control unit 110 provides logic to operate and control one or more I / O devices 112 and adapts, through the use of common mechanisms, the characteristics of each I / O device 112 to the link interface provided by channel 124. The common mechanisms provide for the execution of I / O operations, indications regarding the status of the I / O device 112 and the control unit 110, the control of the timing of data transfers through the channel path 122 and certain control levels of the I / O device 112.

Each control unit 110 locks, via a connection 126 (eg, a bus) to one or more I / O devices 112. I / O devices 112 receive information or store information in memory

ES 2 359 614 T3 main 102 and / or other memory. Examples of I / O devices 112 include card readers and punches, magnetic tape drives, direct access storage devices, displays, keyboards, printers, pointing devices, teleprocessing devices, communication controllers, and computer-based devices. in sensors, to name a few.

One or more of the above components of the I / O processing system 100 are further described in "IBM® z / Architecture Principles of Operation", publication No. SA22-7832-05, 6^to Edition, April 2007; US Patent No. 5,461,721 entitled "System For Transferring Data Between I / O Devices And Main Or Expanded Storage Under Dynamic Control Of Independent Indirect Address Words (IDAWS)", Cormier et al., Issued October 24, 1995; and US Patent No. 5,526,484 entitled "Method And System For Pipelining The Processing Of Channel Command Words", by Casper et al., issued June 11, 1996. IBM is a registered trademark of International Business Machines Corporation, Armonk, New York, USA. Other names used in this document may be registered trademarks, trademarks, or product names of International Business Machines Corporation or other companies.

In one embodiment, to transfer data between I / O devices 112 and memory 102, channel command words (CCWs) are used. A CCW specifies the command to execute, and includes other fields to control processing. An example of a CCW is described with reference to FIG. 2A. A CCW 200 includes, for example, a command code 202 that specifies the command to be executed (eg, read, read back, control, detect, and write); a plurality of flags 204 used to control I / O operation; for commands specifying data transfer, a count field 206 specifying the number of bytes in the storage area designated by the CCW to be transferred; and a data address 208 that points to a location in main memory that includes the data, when using direct addressing, or to a list (eg, contiguous list) of modified indirect data address words (MIDAWs) to be processed. , when using indirect and modified data addressing. Modified indirect targeting is further described in US patent application published number 2008/0043563, entitled “Flexibly Controlling The Transfer Of Data Between Input / Output Devices And Memory,” Brice et al., filed August 15, 2006.

One or more CCWs arranged for sequential execution form a channel program, also referred to herein as a CCW channel program. The CCW channel program is configured, for example, by an operating system, or other software. The software configures the CCWs and obtains the memory addresses assigned to the channel program. An example of a CCW channel program is described with reference to FIG. 2B. A CCW channel program 210 includes, for example, a scoping CCW 212 having a pointer 214 to a memory location of scoping data 216 to be used with the scoping command. In this example, an in-channel transfer (TIC) 218 ​​follows the scoping command, which forwards the channel program to another memory area (for example, an application area) that includes one or more other CCWs. such as a register location 217 having a pointer 219 to register location data 220, and one or more read CCWs 221. Each read CCW 220 has a pointer 222 to a data area 224. The data area includes an address to directly access the data or a list of data address words (eg, MIDAWs or IDAWs) to indirectly access the data. In addition, the CCW channel program 210 includes a predetermined area in the channel subsystem defined by the device address called the subchannel for status 226, resulting from the execution of the CCW channel program.

The processing of a CCW channel program is described with reference to FIG. 3, as well as referring to FIG. 2B. In particular, FIG. 3 shows an example of the various exchanges and sequences that occur between a channel and a control unit when a CCW channel program is running. The link protocol used for communications is, in this example, FICON (Fiber Connectivity). In “Fiber Channel Single Byte Command Code Sets-3 Mapping Protocol” (FC-SB-3), T11 / Project 1357-D / Rev. 1.6, INCITS (March 2003) describes information regarding FICON.

Referring to FIG. 3, a channel 300 opens an exchange with a control unit 302 and sends a scoping command and associated data 304 to the control unit 302. The command is retrieved from scoping CCW 212 (FIG. 2B) and data is obtained from scoping data area 216. Channel 300 uses TIC 218 to locate the register location CCW and the read CCW. It retrieves the record location command 305 (FIG. 3) from the record location CCW 217 (FIG. 2B) and obtains the data from the record location data 220. Read command 306 (FIG. 3) is retrieved from read CCW 221 (FIG. 2B). Each of them is sent to the control unit 302.

Control unit 302 opens an exchange 308 with channel 300, in response to the open exchange of channel 300. This can occur before or after the locate command 305 and / or read command 306. Along with the open exchange, a response (CMR) is forwarded to channel 300. The CMR provides an indication to channel 300 that control unit 302 is up and running.

The control unit 302 sends the requested data 310 to the channel 300. Additionally, the control unit 302 provides the status to the channel 300 and closes the exchange 312. In response thereto, the channel 300 stores the data, examines the status and closes exchange 314, which indicates to control unit 302 that the status has been received.

ES 2 359 614 T3

Processing of the above CCW channel program to read 4k of data requires opening and closing of two exchanges and seven sequences. The total number of exchanges and sequences between the channel and the control unit is reduced through the compaction of multiple orders of the channel program in a TCCB. Channel, eg, channel 124 of FIG. 1, uses a TCW to identify the location of the TCCB, as well as locations to access and store the status and data associated with the execution of the channel program. Channel 124 interprets TCW and it is not sent or viewed by control unit 110.

It is described, with reference to FIG. 4, an example channel program for reading 4k of data, as in FIG. 2B, but that includes a TCCB, rather than separate individual CCWs. As shown, a program 400, referred to herein as a TCW channel program, includes a TCW 402 that specifies a memory location of a TCCB 404, as well as a memory location of an area 406. data or a TIDAL 410 (ie, a list of transport mode data indirect address words (TIDAWs), similar to MIDAWs) pointing to data area 406, and to a status area 408.

The processing of a TCW channel program is described with reference to FIG. 5. The link protocol used for these communications is, for example, the Fiber Channel Protocol (FCP). In particular, three phases of the FCP handshake are used, which allow the use of host bus adapters supporting FCP to perform data transfers controlled by CCWs. FCP and its phases are further described in “Information Technology - Fiber Channel Protocol for SCSI, Third Version (FCP-3)”, T10 Project 1560-D, Revision 4, September 13, 2005.

Referring to FIG. 5, a channel 500 opens an exchange with a control unit 502 and sends the TCCB 504 to the control unit 502. In one example, the TCCB 504 and a sequence initiative are transferred to the control unit 502 in an FCP command, referred to as an FCP_CMND information unit (UI) or a transport order UI. The control unit 502 executes the multiple commands of the TCCB 504 (eg, scope definition command, register locate command, read command as device control words (DCWs)) and forwards data 506 to channel 500 via For example, from a FCP_Data UI. It also provides the status and closes the 508 exchange. As an example, the final state is sent in an FCP status frame that has an active bit, for example, in byte 10 or 11 of the payload of an FCP_RSP UI, also referred to as a response UI Of transport. The FCP_RSP_IU payload can be used to carry the FICON completion status along with additional status information.

In another example, to write 4k of client data, channel 500 uses the FCP handshake phases, as follows:

1. Transfer a TCCB in the FCP_CMND UI.

2. Transfer the data UI, and the sequence initiative to the control unit 502. (FCP Transfer Ready, Disabled).

3. The final state is sent in an FCP status frame that has one bit set, for example, in byte 10 or 11 of the FCP_RSP UI Payload. The FCP_RES_INFO field or detection field is used to carry the FICON completion status along with additional status information.

By executing the TCW channel program of FIG. 4, there is only one open and closed exchange (see also FIG. 5), instead of two exchanges for the CCW channel program of FIG. 2B (see also FIG. 3). Furthermore, for the TCW channel program, there are three communication sequences (see FIGS. 4 and 5), compared to the seven sequences for the CCW channel program (see FIGS. 2B to 3).

The number of exchanges and sequences remain the same for a TCW channel show, even if additional orders are added to the show. Compare, for example, the CCW channel program communications of FIG. 6 with the TCW channel program communications of FIG. 7. In the CCW channel show of FIG. 6, each of the commands (for example, scope definition order 600, record location order 601, read order 602, read order 604, read order 606, record location order 607, and record location order 608 read) is sent in separate sequences from channel 610 to control unit 612. In addition, each block of 4k data (eg, data 614 to 620) is sent in separate sequences from control unit 612 to channel 610. This CCW channel program requires the opening and closing of two exchanges (eg, opening exchanges 622, 624 and closing exchanges 626, 628), and fourteen communication sequences. This is in contrast to the three streams and the single swap for the TCW channel program of FIG. 7, which achieves the same function as the CCW channel program of FIG. 6.

As depicted in FIG. 7, a channel 700 opens an exchange with a control unit 702 and sends a TCCB 704 to the control unit 702. The TCCB 704 includes the scope definition command, the two record location commands, and the four read commands in DCWs, as described above. In response to receiving the TCCB 704, the control unit 702 executes the commands and sends, in a single sequence, the 16k of data 706 to channel 700. Additionally, the control unit 702 provides the status to channel 700 and closes the exchange 708. Thus, the TCW channel program requires far fewer communications to transfer the same amount of data than the CCW channel program of FIG. . 6.

ES 2 359 614 T3

Returning next to FIG. 8, an embodiment of channel 124 in channel subsystem 108 and control unit 110 and channel 124 of FIG. 1 that support TCW channel program execution. Control unit 110 includes CU control logic 802 for parsing and processing command messages containing a TCCB, such as TCCB 704 of FIG. 7, received from channel 124 through connection 120. CU control logic 802 can extract DCWs and control data from the TCCB received at control unit 110 to control a device, eg, I / O device 112 through connection 126. Control logic 802 from the CU sends device commands and data to the I / O device 112, and receives status information and other feedback from the I / O device 112. For example, the I / O device 112 may be busy due to a pre-reservation request directed to the I / O device 112. To manage potential device reservation contention problems that may arise when the control unit 110 receives multiple requests to access the same I / O device 112, the CU control logic 802 keeps track of and stores busy messages. regarding devices and associated data in a busy device queue 804. In an exemplary embodiment, an OS 103 of FIG. 1 reserves the I / O device 112 to prevent other OSs 103 from accessing the I / O device 112 while the reserve is active. Although device reservation is not required for all I / O operations, device reservation can be used to support operations that require exclusive access for a fixed period of time, for example, a disk format.

Control unit 110 may further include other buffer or memory elements (not shown) for storing multiple messages or status information associated with communications between channel 124 and I / O device 112. For example, a register located in control unit 110 may include a control unit maximum exchanges parameter that defines the maximum number of control unit open exchanges that control unit 110 supports.

Channel 124 in channel subsystem 108 includes multiple elements to support communication with control unit 110. In an exemplary embodiment, CHN control logic 806 controls communication between channel subsystem 108 and control unit 110. CHN control logic 806 can interface directly with CU control logic 802 through connection 120 to send commands and receive responses, such as transport order and response IUs. Alternatively, between the CHN control logic 806 and the CU control logic 802 can be located buffers and / or message interfaces (not shown).

In FIG. 9 depicts an exemplary embodiment of a transport control word (TCW) 900. TCW 900 is used by channel 124 to configure I / O operation and is not sent to control unit 110. The TCW depicted in FIG. 9 provides for both input and output data in a single I / O operation.

In an exemplary TCW 900 depicted in FIG. 9, a field 902 of format equal to "00b" indicates that what comes next is a TCW 900. The TCW 900 also includes reserved bits 904 for possible future use.

The TCW 900 also includes a flag field 906. The first five bits of the flag field 906 are reserved for future use and are set to zero. The sixth bit of the flag field 906 is a TIDAL read flag. In an exemplary embodiment, the TIDAL read flag is set to one when the input data address field 918 contains an address of a TIDAL. If the TIDAL read flag is set to zero, then the input data address field 918 contains a data address. The seventh bit of the flag field 906 is a TIDAL TCCB flag. In an exemplary embodiment, the TIDAL TCCB flag is set to one when the TCCB address field 922 contains an address of a TIDAL. If the TIDAL TCCB flag is set to zero, then the TCCB address field 922 addresses the TCCB directly. The TIDAL TCCB flag allows hypervisor or operating system software to layer and prefix user channel programs. The eighth bit of the flag field 906 is a TIDAL write flag. In an exemplary embodiment, the TIDAL write flag is set to one when the output data address field 916 contains an address of a TIDAL. If the TIDAL write flag is set to zero, then the output data address field 916 contains a data address.

The ninth through twenty-fourth bits of the flag field 906 are reserved for future use.

The TCW 900 also includes a TCCB length field 910 that indirectly represents the length of the TCCB and can be used to determine the actual length of the TCCB.

The read / write bits 912 on the TCW 900 are used to indicate whether data is being read and / or written as a result of executing the TCW 900. In an exemplary embodiment, the read bit in the read / write bits 912 is set to one to indicate that input data is being transferred from an I / O device 112 to a system storage media (e.g., the main memory 102) on host system 101 as a result of running TCW 900. The write bit in the read / write bits 912 is set to one to indicate that output data is being transferred from a system storage media (eg, main memory 102) in host system 101 to a storage device. I / O as a consequence of running the tCw 900.

The output data address field 916 includes the address for the output data (if any). As previously described, the content of the output data address field 916 may be a

ES 2 359 614 T3 address of a TIDAL for output data (eg an indirect address) or the actual address of the output data (eg a direct address). The input data address field 918 includes the address for the input data (if any). As previously described, the content of the input data address field 918 may be an address of a TIDAL for input data or the actual address of the input data. In an exemplary embodiment, the output data address field 916 and the input data address field 918 are implemented as sixty-four bit addresses.

The TCW 900 also includes a transport status block address field 920. At this address, a portion (for example, the extended status part) of a completion status is stored in a transport response UI for an I / O operation. The TCCB address field 922 in the TCW 900 includes an address at which the TCCB is located on the storage media of the system. As previously described, the TCCB is the control block in which the DCWs to be executed for the TCW 900 reside. As previously also described, the content of the TCCB address field 922 can be a address of a TIDAL for the TCCB or the actual address of the TCCB. In an exemplary embodiment, the transport status block address field 920 and the TCCB address field 922 are implemented as sixty-four bit addresses.

The output count field 924 on the TCW 900 indicates the amount of output data to be transferred by the TCW / TCCB for an output operation. In an exemplary embodiment, the output count field 924 specifies the number of bytes in the output storage area designated by the TCW (the output data address 916) to transfer. The input count field 926 in the TCW 900 indicates the amount of input data to be transferred by the TCW / TCCB for an input operation. In an exemplary embodiment, the input count field 926 specifies the number of bytes in the output storage area designated by the TCW (the input data address 918) to transfer. In TCW 900, several additional fields are reserved: reserved field 928, reserved field 930, and reserved field 932. The interrogation TCW address field 934 contains the address of another TCW and is used by channel 124 to interrogate that state of an operation at the initiative of a cancel subchannel I / O instruction.

The TCW depicted in FIG. 9 is an example of how a command word can be configured. Other configurations are possible in which additional fields are included and / or fields shown in FIG are not included. 9.

FIG. 10 depicts an embodiment of a TCW channel program, according to one aspect of the present invention when both input and output data are included in a single I / O operation. As shown in FIG. 10, a TCW channel program 1000 includes a TCW 1002 that specifies a memory location of a TCCB 1004, a memory location for storing input data 1006, or a TIDAL 1010 (that is, a list of indirect address words from transport mode data (TIDAWs) that points to the location for input data 1006, a memory location of an output data area 1014 or a TIDAL 1012 that points to output data area 1006, and an area 1008 of condition.

It is described with reference to FIG. 11 the processing of the TCW channel program 1000 depicted in FIG. 10. Referring to FIG. 11, a channel 1100 opens an exchange with a control unit 1102 and sends a TCCB 1104 and output data 1105 located in the output data area 1014 specified by TCW 1002 to the control unit 1102. Channel 1100 determines how much data to send based on the value of output count 924 in TCW 1002. The control unit 1102 executes the multiple commands from the TCCB 1104 (for example, scope definition order, register locate order, write order, and read order as device control words (DCWs)) receives data 1105 from output channel 1100 and forwards input data 1106 according to the data count in the DCW to channel 1100 through, for example, a FCP_Data UI. Channel 1100 stores input data 1106 at the position specified by TCW 1002. Control unit 1102 also provides status and closes exchange 1108. In this way, data is input to channel 110 and output. to the control unit 1102 in a single TCW channel program 1000 (or I / O operation).

FIG. 12 depicts one embodiment of a process for bidirectional transfer of data in a single I / O operation, according to one aspect of the present invention. In an exemplary embodiment, the processing depicted in FIG. 12 occurs in a host computer system that is in network communication with a control unit. The host computer system may include an I / O processing system that executes the process. Additionally, the I / O processing system may include a channel subsystem that executes the process. At block 1202, the host computer obtains a TCW. In an exemplary embodiment, the TCW is obtained (or received) from an operating system running on the host computer. The TCW includes both an output data address 916 and an output count field 924 and an input data address 918 and an input data count field 926. In an exemplary embodiment, the TCW includes output data when the write bit in the read / write bits 912 is set to one and the TCW includes input data when the read bit in the read / write bits 912 is set. to one. At block 1204, the TCCB position specified by TCW 922 is retrieved and forwarded to the control unit. The TCCB contains the DCWs that inform the control unit which I / O operations to execute.

In block 1206, the output data is collected from the position specified by the TCW (if the

ES 2 359 614 T3 writing to the read / write bits 912 is set to one). The amount of collected data to include in the output data is based on the value of the output data count field 924. As previously described, the output data address can be a direct output data address or an indirect output data address. An indirect address refers to an address that contains a list of one or more addresses (eg, a TIDAL) that point to a plurality of storage locations that collectively constitute the output data. A direct address refers to an address that contains the output data. In an exemplary embodiment, the TIDAL write flag in TCW flag field 906 is set to one when the output data address field 916 contains an address of a TIDAL, and is set to zero when field 916 output data address contains the address of the output data.

At block 1208, the output data is forwarded to the control unit. For this example, XFER_RDY is disabled.

At block 1210, input data is received from the control unit as a consequence of executing the I / O operation. At block 1212, the input data is stored at the location specified by the TCW (the input data address 918). In an exemplary embodiment, the TCW includes input data when the read bit in the read / write bits 912 is set to one. As previously described, the input data address 918 may be a direct address for storing the input data, or alternatively it may be an address to a list of addresses (eg, a TIDAL or an indirect address) pointing to a plurality of storage locations, each storing portions of the input data. In an exemplary embodiment, the TIDAL read flag in TCW flag field 906 is set to one when input data address field 918 contains an address of a TIDAL, and is set to zero when field 918 input data address contains the address of the input data.

The technical effects of the exemplary embodiments include the ability to include both input and output data in a single I / O operation. This provides flexibility in grouping DCWs and can lead to a reduction in the number of exchanges required between a channel and a control unit.

As described above, the embodiments can be embodied in the form of computer-implemented processes, and apparatus for carrying out those processes. In exemplary embodiments, the invention is embodied in computer program code executed by one or more network elements. Embodiments include a computer program product 1300 as depicted in FIG. 13 on a computer usable carrier 1302, with computer program code logic 1304 containing instructions embodied on tangible carriers such as an article of manufacture. Exemplary articles of manufacture such as computer-usable media 1302 may include floppy disks, CD-ROMs, hard drives, universal serial bus (USB) type flash drives, or any other computer-readable storage media, where When the logic 1304 of the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for carrying out the invention. Embodiments include computer program code logic 1304, for example, either stored on a storage medium, loaded into and / or executed by a computer, or transmitted via some transmission medium, such as via electrical wires or wiring, through fiber optics, or through electromagnetic radiation, wherein, when computer program code logic 1304 is loaded into and executed by a computer, the computer becomes an apparatus for putting the invention into practice. When implemented in a general purpose microprocessor, segments of computer program code logic 1304 configure the microprocessor to create specific logic circuits.