JPS62256154A - Channel path control system - Google Patents

Abstract

PURPOSE:To simply cancel a CU busy or unit check condition which is not cancelled but remains by detecting a time-out when the activation is applied for a channel path unit and recognizing that a path busy condition or the like is left and resetting the condition by a channel processor. CONSTITUTION:When the channel processor 3 checks whether the activation can be executed to an I/O device 10 or not, it refers to a control word 12. At this time, when the presence of the unit check condition is recognized, the channel processor 3 recognizes that this condition is maintained for more than a constant time by the value of a time stamp 16. Further, the channel processor 3 checks whether a sense time out function is provided or not in a control unit by a control bit 13 and if this control bit is turned ON, a control bit 15 is reset and the control unit can be used by the I/O device 10.

Description

[Detailed Description of the Invention] [Summary] Cυ busy and other bus busy conditions are recognized by detecting a timeout when each channel bus is activated, and the channel processing device This is a channel path control method that resets conditions.

[Industrial application field]

The present invention provides a computer system, particularly a channel processor f! provided separately from a central processing unit. ! This invention relates to a channel/path control method in large-scale computer systems, etc., in which channels and paths are managed in devices.

[Conventional technology]

A physical and logical communication path used for data transfer and control leading to individual I/O devices is called a channel bus. Currently, the mainstream technology is to offload the state management and control of these paths to the channel processing 22, which exists independently from the central processing unit. However, in today's complex I/O configurations in which multiple channels are connected to multiple control units, and the control units are also connected to multiple I/O devices, individual I/O /O
Channel paths leading to a device cannot be used completely independently of each other. For example, a certain I/O
A so-called "unit check" condition has occurred in a device, and the type of control unit is such that it cannot service other I/O devices connected to the control unit until the condition is removed. If so, other I/O operations will be disabled until this condition is removed.
No service initiation instructions for the device should be generated from the channel processor.

However, in the above example, the central processing unit recognizes that the unit check condition has occurred and instructs the channel processing unit to perform appropriate processing, and as a result of that processing, this condition is removed. This is normally expected, but there may be cases where the processing for canceling these conditions is not executed normally for some reason, or the processing is not performed by the program running on the central processing fr1 device. Depending on the cause, this condition may not be lifted.

Also, for example, when a control unit responds to a so-called CU busy condition in response to activation from a channel processing device, for reasons of efficiency, the control unit waits until a CU end report, which is a signal to cancel the condition, is sent from the control unit. If a channel processing device performs control that causes startup processing for I/O devices under the control unit to wait, the CU end condition will be lost due to a temporary error on the control unit side or channel side. If this happens, the I/O device under that control unit will lose at least one communication path.

[Problem to be solved]

In order to release the CU busy or unit check condition that remains unresolved as described above, periodically scan the control unit 7 and check the CU busy or unit check condition that remains unresolved. - Although it is possible to cancel the check condition, this method has the disadvantage that the burden on the channel processing device increases significantly.

The present invention was created in view of these points, and it is possible to easily cancel the CU busy and unit check conditions that remain unreleased, and also to prevent communication with I/O devices. The purpose of this study is to provide a channel path control method that allows the network to be quickly secured.

[Means for solving problems]

FIG. 1 is a diagram showing an example of an input/output system to which the present invention is applied, and FIG. 2 is a diagram showing an example of the configuration of a control word. In the figure, 1 is a central processing unit, 2 is a storage control unit, 3 is a channel processing unit, 4 to 7 are channels, 8 is a control unit, 9 and /O are I/O devices, and 11 is a channel processing unit 3. Local storage, 12 is a control word, 13 is a control bit indicating the type of control unit, 14 is a control bit indicating that a cU busy condition is held, 15 is indicating a unit check condition is being held. Control bits 16 each indicate a timestamp.

When an I/O command is issued from the central processing unit f, the subchannel corresponding to the target device is changed according to the command and connected to various types of queues. Thereafter, the channel processing device 3 dequeues the subchannel from this queue asynchronously with this I/O command and attempts processing. If any condition is detected there, the subchannel is re-enqueued. The control word 12 corresponds to the control unit 8 and is present in the local storage 11 of the channel processing device 3.

The control word 12 has a control bit 13 indicating the type of control unit 8, a control bit 14 indicating whether the CU is busy, a control pin 15 indicating whether a unit check condition has occurred, and a timestamp 16. ing. Timestamp 16 indicates CU busy or unit
This indicates the time when the check occurred. Both CU busy and unit check recontrol are set/reset by the channel processing device 3. The time stamp value is rewritten each time a unit check is detected. C
Except for the present invention, U-busy is released at the following timing.

■ When a device reports status including Control Unit End (CUIE).

■ C5CII (C1ear 5ubchannel)
When the control unit is reset by command.

■ When the channel processing unit 3 detects some error and the control unit is reset as a result.

In the present invention, when a device connected to the control unit attempts to use this path and detects a CU busy, the time stamp is checked. At this time, if the bit is greater than a certain period of time, the CU busy flag is reset on the spot.

Suppose now that a unit check condition occurs in the I/O device 9. The operating system running on the central processing unit 1 attempts to issue a sense command to this I/O device 9, but due to an error in the I/O device 9, the unit issues the unit again in response to this sense command. Suppose that a check condition occurs.

In this environment, the contents of the control word 12 should be set as follows. That is, the control bit 15 indicating that the unit check condition exists is turned on, and the time stamp 16 records the time when the unit check condition occurred in response to the sense instruction.

Normally, the channel processing device 3 does not attempt to start a control unit whose unit check condition is maintained. Therefore, if the central processing unit 1 tries to start up the device /O, the channel processing unit 3
In this case, this activation is blocked. Channel processing device 3
waits for the next sense instruction to be issued if the unit check condition occurs.

However, if a unit check occurs for the sense, O3 may give up reaping this condition in some cases.

In such a case, if the present invention is not employed, this condition will not be cleared and will remain held in the control word 12. Therefore, activation of I/O devices/Os under the same control unit will have to wait. This is because the control unit 8 has a so-called sense timeout function, that is, if the unit check condition is not cleared by the host device for a certain period of time, the control unit itself is in a state where it can service other devices. The same is true even if the function of returning is provided.

In the present invention, control is performed as follows. The channel processing device 3 uses the control word 12 when checking whether activation of the I/O device/O is possible.
See. At this time, when it is determined that one unit check condition exists, the channel processing device 3 recognizes from the value of the timestamp 16 that this condition has been held for a certain period of time or longer. Furthermore, the channel processing device 3 checks whether this control unit is equipped with a sense timeout function using the control bit 13, and if this control bit is ON, it resets the control bit 5 and sets this control unit to・I/the unit
O device/O can be used.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, CU busy and unit check conditions that remain unreleased because no event to release them have occurred can be handled with relatively simple processing. Can be canceled.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of an input/output system to which the present invention is applied, and FIG. 2 is a diagram showing an example of the configuration of a control word of the present invention. 1...Central processing unit, 2...Storage control device, 3...
・Channel processing device, 4 to 7...channel, 8・
...Control unit, 9 and /O...I'/
O device, 11... Local storage, 12... Control word 12.13... Control bit indicating the type of control unit, 14... Control bit indicating that the CU busy condition is held. 15... Control bit indicating that the unit check condition is maintained, 16... Time stamp. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney: Kyotani, Part 4, Figure 1, Figure 2

Claims (1)

[Claims] In a computer system in which the state of communication paths between an I/O device and the central processing unit is managed by a channel processing unit that exists separately from the central processing unit, the state of each communication path is managed by a channel processing unit that is separate from the central processing unit. A condition that restricts the operation of the device has occurred. Storage management is performed in response to physical resources shared with other devices, and operation is restricted due to the occurrence of a condition that restricts the operation of other I/O devices. Duration of state from the time when a state occurs where the channel processing device restricts the operation of another I/O device due to an attempt by another I/O device to use the physical resource and a channel path control method characterized in that the contents of the state are analyzed, and if the conditions are satisfied, the state is canceled even if an event that should originally cause the state to be canceled has not occurred.