JPH0572617B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] The channel processing device recognizes that CU busy and other path busy conditions are left behind by detecting a timeout when each channel path is activated. This is a channel path control method that resets the conditions.

[Industrial application field]

The present invention relates to a computer system, and particularly to a channel/path control method in a large-scale computer system where channel paths are managed in a channel processing unit provided separately from a central processing unit.

[Conventional technology]

The physical and theoretical communication paths used for data transfer and control that lead to individual I/O devices are called channel paths. Currently, the mainstream technology is to offload the state management and control of these paths to a channel processing device that exists independently from the central processing device. However,
In today's complex I/O configurations, where multiple channels are connected to multiple control units, and the control units are also connected to multiple I/O devices, individual I/O
Channel paths leading to a device cannot be used completely independently of each other. For example, in a certain I/O device, the so-called "unit
CHECK” condition occurs and the type of control unit is such that it cannot service other I/O devices connected to it until the condition is removed. No service initiation instructions for other I/O devices should be issued from the channel processor until released.

However, in the above example, the unit
In the normal case, it is expected that the central processing unit recognizes that a check condition has occurred, instructs the channel processing unit to perform appropriate processing, and that the condition is canceled as a result of that processing. However, this condition may be canceled due to reasons such as the processing to cancel these conditions not being executed normally for some reason, or the processing being not performed by the program running on the central processing unit. There may be cases where it is not released.

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

[Problem to be solved]

In order to clear the CU busy and unit check conditions that remain as described above, the control unit is periodically scanned and the CU that remains uncleared is scanned.
It is also possible to cancel the busy or unit check condition, but this method has the drawback of significantly increasing the load on the channel processing device.

The present invention was created in view of these points, and the present invention was created in view of the above points, and the present invention
It is an object of the present invention to provide a channel path control method that can easily release busy and unit check conditions, and can quickly secure a communication path to an I/O device.

[Means for solving problems]

The channel path control method of the present invention includes a channel processing device, a channel connected under the channel processing device, a control device connected under the channel, and an input/output device connected under the control device. This assumes a computer system equipped with

When a short-term condition from a controller that blocks the controller, such as controller busy or unit check, is sent to the channel processor,
The occurrence of a short-term condition that blocks the control device is written in the control information storage memory area corresponding to the control device provided in the storage section of the channel processing device, and the time of occurrence is written in the storage section of the channel processing device. is written to the time stamp memory area corresponding to the control device. A short-term condition that blocks a control device is a condition that makes it impossible for the control device itself to operate on multiple I/O devices under the control device, and is usually caused by software running on a host computer. This term refers to a condition that is expected to be quickly cleared due to processing on the hardware side or a change in the situation inside the I/O device or the control device that occurs in a short period of time.

When determining whether a channel processing device should issue a request to a control device, it refers to the control information storage memory area and time stamp memory area corresponding to the control device, and stores the above information in the control information storage memory area. If a short-term condition for blocking the control device is entered, the above-mentioned reset condition is satisfied, including at least that the short-term condition for blocking the control device exists for a certain period of time or more. A request is issued after resetting the short-term conditions that block the control device.

〔Example〕

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 the central processing unit, 2
is a storage control device, 3 is a channel processing device, 4 to 7 are channels, 8 is a control unit,
9 and 10 are I/O devices, 11 is local storage of the channel processing device 3, 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 maintained, 15 is a control bit indicating that a unit check condition is maintained, 1
6 indicates a time stamp.

When an I/O command is issued from the central processing unit 1, the subchannel corresponding to the target device is changed according to the command and connected to a certain type of queue. Thereafter, the channel processing device 3 dequeues a subchannel from this queue asynchronously with this I/O command and attempts processing. If any busy condition is detected there, the subchannel will be re-enqueued. Control word 12 corresponds to control unit 8;
It resides in the local storage 11 of the channel processing device 3. Control word 12 includes control bits 13 indicating the type of control unit 8;
It has a control bit 14 indicating whether the CU is busy, a control bit 15 indicating whether a unit check condition has occurred, and a timestamp 16.
The timestamp 16 indicates the time when CU busy or unit check occurred.
Both CU busy and unit check controls are set/reset by the channel processing device 3. The time stamp value is rewritten each time a unit check is detected. In the conventional technology, CU busy is released only at the following timings.

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

When the control unit is reset by the CSCH (Clear Subchannel) command.

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

In the present invention, devices connected to the control unit attempt to use this path,
When a CU busy is detected, the time stamp is checked. At this time, the time that the CU busy stays is calculated from the time recorded in the time stamp, and if this time is longer than a certain fixed 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. - Assume that a check condition occurs.

In this environment, the contents of the control word 12 should be set as follows. That is, control bit 15, which indicates that the unit check condition exists, is ON, and timestamp 16 is ON.
The time at which the unit check condition occurred in response to the sense instruction is entered in .

Normally, the channel processing device 3 does not attempt to start a control unit for which a unit check condition is maintained. Therefore, even if the central processing unit 1 attempts to activate the device 10, the channel processing unit 3 will prevent this activation. When a unit check condition occurs, the channel processing device 3 waits for the next sense command to be issued. However, if a unit check occurs for the sense, in some cases the OS may give up on reaping this condition.

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, I/O devices 10 under the same control unit
The startup 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 can service other devices. The same is true even if there is a function to return to a normal state.

In the present invention, control is performed as follows. The channel processing device 3 is an I/O device 10
The control word 12 is referenced when checking whether activation is possible. At this time, if the existence of the unit check condition is found, the channel processing device 3 recognizes from the value of the timestamp 16 that this condition has been maintained for a certain period of time or more. Furthermore, the channel processing device 3 checks whether this control unit is equipped with a sense timeout function by means of control bit 13, and if this control bit is ON, resets control bit 15. , which allows the I/O device 10 to use this control unit.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, CU busy and unit check conditions that remain unreleased because no event to release them occurs can be cleared by relatively simple processing. You can.

[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 devices, 4 to 7 ... Channels, 8 ... Control units, 9 and 10 ...
...I/O device, 11 ...Local storage, 12
...Control word, 12,13...Control word
Control bits indicating unit type, 14...
Control bit indicating that the CU busy condition is held; 15...Control bit indicating that the unit check condition is being held; 16...Time stamp.

Claims (1)

[Claims] 1. A channel processing device, a channel connected under the channel processing device, a control device connected under the channel, and an input/output device connected under the control device. In a computer system, when a short-term condition that blocks the control device, such as a control device busy or unit check, is sent from a certain control device to the channel processing device, a short-term condition that blocks the control device occurs. The occurrence time is written in the control information storage memory area corresponding to the control device provided in the storage section of the channel processing device, and the time of occurrence is written as a time stamp corresponding to the control device provided in the storage section of the channel processing device. When the channel processing device decides whether to issue a request to the control device, it refers to the control information storage memory area and the time stamp memory area corresponding to the control device, and writes the control information to the memory area. If a short-term condition for blocking the control device is written in the storage memory area, the reset condition at least including that the short-term condition for blocking the control device exists for a certain period of time or more is satisfied. A channel path control method characterized in that, on the condition that the short-term condition that blocks the control device is reset, a request is issued.