JPS59161717A - Priority decision system - Google Patents

Abstract

PURPOSE:To use an external storage device in common by giving priority between a magnetic tape device which has a short execution time for an input or output instruction and a magnetic tape device which has a long execution time for the input or output instruction. CONSTITUTION:When a magnetic disk device 4 is selected by an external storage controller 3, there is an instruction which is executed only by the controller, so while the device 4 executes the instruction, the device 3 executes the input or output instructions of a magnetic tape device 5. When, however, the controller 3 executes the input or output instruction of the device 5, the device 4 couples with a host device again to prevent the execution of the next instruction, so there is the possiblity of a time-out state. For this purpose, when an input or output instuction arrives at the device 5, a microprocessor 13 checks a bit of a register 14 corresponding to the device 4 through a multiplexer 12 and informs the host device that the controller is in use through a register 7 when the bit is on, and the software of an electronic computer processing system 1 or 2 is retried to execute the instruction of the device 5 after the instruction of the device 4 is executed.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to an external storage control device that is connected to and controlled by a computer processing system and that connects and controls multiple types of external storage devices, and particularly relates to The present invention relates to a priority determination method for controlling input/output commands given to each external storage device when controlled by an electronic computer processing system.

(b) Prior art and problems Multiple external storage devices consisting of magnetic disk devices, magnetic tape devices, etc. are controlled by one external storage control device, and a host device randomly controls the magnetic disk devices and magnetic tape devices. When an input/output command is given to a device, some of the input/output commands can be executed only by the controlled device, such as a magnetic tape device or a magnetic disk device. For example, 1. seek head, cent sector, +
- When the commands ``chiiD'' and ``read'' are chained and instructed, commands such as ``reseek head 1'' and ``sent sector'' can be executed by the magnetic disk device alone. While the magnetic disk device is executing such an instruction, the external storage control device can execute input/output instructions to other external storage devices.

Therefore, if an input/output command is executed for the magnetic tape device at this time, the execution time of the instruction for the 5 magnetic tape device will be long (
, especially when there is a long interblock gap, it takes time to detect lightning. During this time, the magnetic disk device completes the execution of the above command, reports the completion to the external storage control device, reconnects with the host device, and stores the target Zarch iD.
, an attempt is made to execute a read command, but since the external storage control device controls the magnetic tape device, if the timing of detecting the completion report is inappropriate, the magnetic disk device may not be able to reconnect with the host device at the appropriate time. First, it waits for the disk to rotate. If such a rotation wait occurs many times, the software will time out and the system will go down in the worst case.

In order to avoid the above situation, conventionally, software has been used to execute input/output commands to the magnetic tape device after the request to the magnetic disk device has ceased. However, in the case of an external storage control device that is shared by a plurality of computer processing systems, there is a drawback that software control cannot be performed on the computer processing systems of other systems.

(C) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to solve the problem of the short execution time of input/output commands, which increases the risk of time-out if processing is left waiting. The object of the present invention is to provide a priority determination method that adds priority to a long magnetic tape device and enables common control of an external storage control device shared by a plurality of computer processing systems. .

(d) Structure of the Invention The structure of the present invention is that in an external storage control device that is connected to a computer processing system and has a function of connecting and controlling external storage devices of a type, each of the connected external storage devices Provide a means for remembering that an input/output command is being executed,
If an external storage device with a lower priority among the external storage devices of the access type is selected by the host device, even if the external storage control device is in a state in which input/output commands can be executed, the storage means is given priority. When there is a record that an external storage device with a high priority is executing an input/output command, a report indicating that the control unit is in use is returned to the host device, giving priority to the execution of the input/output command of the external storage device with a high priority. be.

(e) Embodiments of the Invention In order to achieve the above object, the present invention provides an external storage control device for a magnetic disk device and a magnetic tape device.

A register is provided to store input/output command reception.

When a plurality of commands are instructed to the magnetic disk device in a chain, the register records that the input/output command is being executed, and the memory is erased when the series of input/output commands is completed. , during the execution of a series of instructions, external memory f, e?
liη When the control device becomes temporarily free, even if there is an input/output command to the magnetic tape device, a report indicating that the control device is in use is returned, and the input/output command to the magnetic tape device is made to wait. It is.

FIG. 1 shows an example of the configuration of a system to which the present invention is applied.

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention. The computer processing system 1.2 is connected to the ink face of the external storage control device 3 via a channel, and data is transferred to the magnetic disk device 4 and the magnetic tape device 5 via the external storage device N3. The present invention relates to a control priority determination system in the external storage control device 3, and FIG. 2 shows an outline of a circuit within the external storage control device 3.

A control signal is input from the channel of the host device to the register 6 through the interface. The control signal enters the microprocessor 13 via multiplexer 12 and is decoded. A control signal sent from the microprocessor 13 to the host device is sent from the terminal B via the register 7. The machine number of the device that executes the instruction, the instruction, and the amount of data to be written on the medium are input from the terminal C via the register 8, enter the microprocessor 13 via the multiplexer 12, and enter the buffer 15 via the multiplexer 11. When the microprocessor 13 detects the selection signal via the register 6 and the machine number and instruction of the device via the register 8, it decodes the contents, selects an external storage device, and executes the input/output instruction. At this time, if the turnout instruction is executable, the bit corresponding to the controlled device in the register 14 is turned on. The register 14 is a means for storing information that an input/output command is being executed.

The number of focal points is required for the number of external storage devices connected to the external storage control device 3. The data entered in the buffer 15 is sent from terminal E to the controlled device.

醋）Is it better to be controlled than child F? Data read from all devices is entered, stored in a buffer 15 via a multiplexer 11, sent to a register 9 via a multiplexer 10, and transferred to a higher-level device via a terminal.

If the above-mentioned selected controlled device is the magnetic disk device 4, some of the input/output commands can be executed only by the magnetic disk device 4, as described above.

While executing such an instruction, the external storage control device 3 can execute input/output instructions to the magnetic tape device 5, which is another external storage device. However, if an input/output command to the magnetic tape device 5 is executed as in /ψ, it will prevent the M11 disk device 4 from reconnecting with the host device to process the next command, and there is a risk of a time error. Therefore, when an input/output command to a magnetic tape device is received, the microprocessor 13 checks the bit corresponding to the magnetic disk device 4 in the register 14 via the multiplexer 12, and when the bit is on, controls the host device via the register 7. A report of the device in use is sent, and a software installation trial of the computer processing system 1 or 2 is performed.

After all the series of commands for the magnetic disk device 4 are completed, the corresponding bits of the register 14 are turned off and input/output commands for the magnetic tape device 5 are executed.

(f) As described in detail, the present invention is applicable to external storage devices that are randomly accessed, and to magnetic disk devices where the execution time of input/output commands is short and there is a risk of timeout if processing is made to wait. This has a great effect because it adds priority to the magnetic tape device whose input/output commands take a long time to execute, and prevents timeout orders from being placed in the magnetic disk device.

[Brief explanation of drawings]

1- is a diagram showing an example of the configuration of a system to which the present invention is applied, and FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention. 1.2 is an electronic computer processing system, 3 is an external storage 1.9 control device, 4 is a magnetic disk device, 5 is a magnetic tape device,
6.7. &, 9.14 is a register, 13 is a microprocessor, and 15 is a buffer. one

Claims (1)

[Claims] In an external storage control device that is connected to a computer processing system and has the function of connecting and controlling multiple types of external storage devices, an input/output command is being executed for each connected external storage device. If an external storage device with a lower priority among the plurality of types of external storage devices is selected by the host device, the external storage control device is in a state capable of executing an input/output command. Also, if the storage means has a record that an input/output command is being executed by an external storage device with a high priority, a report indicating that the control device is in use is returned to the host device, and the input/output command of the external storage device with a high priority is executed. A priority determination method characterized by prioritizing.