JPH02103619A - Adapter device - Google Patents

Abstract

PURPOSE:To prevent the system down of all host systems due to confliction of instructions issued from each host system by using the identification information of the host system which issues the instruction selected by confliction control as status information and informing all instruction issuing host systems of the status information when occupation continuation canceling instructions are simultaneously issued. CONSTITUTION:When occupation continuation canceling instructions (forcible occupying instructions) are simultaneously issued, the identification information ID of the host system to which access right to an external storage device 5 which is a shared device is permitted by confliction control is noticed to host systems 1-3 to which no access right is permitted by conflict control. Accordingly, each host system 1-3 can recognize whether or not their own forcible occupying instructions become effective and can decide whether the forcible occupying instructions are reissued directly or later during the course of normal operations. Therefore, the system down of all host systems caused by confliction of forcible occupying instructions issued from each host system can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an adapter device added to a shared device such as an external storage device that is accessed from a plurality of host systems. The present invention relates to recovery means when a failure occurs in a shared device that is a resource.

(Prior Art) Fig. 3 shows a conventional system configuration in which an adapter device is added to make an external storage device (for example, a magnetic disk device) as a shared resource accessible from each host system in a triple host system. FIG.

In the figure, 1 to 3 are host systems forming a triple host system, and 4 is an adapter device that allows access from the host systems 1 to 3 to the external storage device 5.

Next, the operation will be explained. First, each of the plurality of host systems 1 to 3 is independent, and each time it becomes necessary to access the external storage device 5, a normal occupancy command is issued to the adapter device 4. The adapter device 4 that has received this occupancy command performs internal competition control, selects the occupancy command for the host system 1 from among the host systems 1 to 3, and restricts access to the external storage device 5 to the host system 1.
allowed. On the other hand, the other host system 2.3 that issued the exclusive command at the same time is notified that the external storage device 5 is already in an occupied state by another host system, and is given the right to access the external storage device @5. not give.

Here, it is assumed that the host system 1 has acquired access rights to the external storage device 5 and is in an exclusive state. In this state, host system 1 has an M source error.

If the system goes down due to a system error, etc., the other host system 2 for the external storage device 5
, 3 is not accepted, the external storage device 5 continues to be occupied via the adapter device 4. At this time, the host systems 2 and 3 other than the host system 1 recognize that the host system 1 is in a system down state because the command is not accepted no matter how long the occupancy command is issued. In order to effectively utilize the shared resources of the external storage device 5 that is continuously occupied by the system 1 or to maintain continuity of system operation, it is necessary to forcefully release the external storage device 5 from the continuously occupied state.

That is, each host system 1 to 3 is stored in the external storage device 5.
Assuming that files such as data and programs essential for the operation of the external storage device 5 are stored therein, if the external storage device 5 falls into an occupied state, a certain period of time after the host system 1 falls into a state where the external storage device 5 continues to be occupied. Other host system 2
．． All three systems go down all at once. Therefore, in order to solve this problem, the adapter device 4 that allows access to the external storage device 5 is forced to release the continuous occupation state of the external storage device 5, so that access to the external storage device 5 can be resumed. It is necessary to maintain continuous system operation. Therefore, among the plurality of host systems 1 to 3, for example, an abnormality in host system 1 causes the external storage device 5 to remain occupied, and when the other host systems 2 and 3 recognize this, the host systems 2 and 3 A forced occupancy command is asynchronously issued to the adapter device 4 in order to release the continued state of occupancy by the host system 1 and acquire access rights. Upon receiving this, the adapter 4 performs internal conflict control, selects the forced occupation instruction for one of the host systems 2 and 3, and accesses the external storage device @5 to the selected host system. give rights.

At this time, other host systems are notified that the host system has already entered the occupied state even though the forced occupation command has been issued.

[Problem to be solved by the invention]

The conventional adapter device is configured as described above.
The host system that issued the forced occupancy command is
15, it is possible to recognize that the forced occupancy command has been effectively processed. However, other host systems for which access rights to the external storage device W15 could not be obtained are only notified that it has already become occupied, so perhaps the forced occupation command itself was not accepted correctly. It is not possible to determine whether the host system has transitioned to the occupied state (normal operation), and as a result, the forced occupation command is repeatedly retried as a recovery process. This retry not only interrupts access to the external storage device 5 of the host system that has started normal operation, causing the host system to go down, but also, in the worst case, results in a forced occupancy command, causing all host systems to There are problems such as the possibility that the system will go down, and the recovery method for the entire system becomes extremely complicated. That is, if host system 2 repeatedly issues forced occupancy commands while host system 1 has acquired access rights, adapter M4 transfers access rights to host system 2 due to contention control, and host system 1 host system 1 becomes system down, and in the worst case, all host systems 1 to 3 issue forced occupancy commands, causing all host systems 1 to become occupied.
There was a problem in that there was a high possibility that the system would go down, and the recovery method for the entire system would be extremely complicated.

This invention was made in order to solve the above-mentioned problems, and it allows the host system that has acquired access rights to access the shared device without interrupting it, and to control the entire system by issuing forced possession commands, etc. An object of the present invention is to provide an adapter device that can prevent system down.

[Means to solve the problem]

The adapter device 4 according to the present invention is configured to issue an instruction (forced occupancy instruction) for forcibly releasing a shared device (external storage device 5) from an occupied state when a plurality of host systems 1 to 3 issue the instruction simultaneously. The commands issued by the host system (forced occupancy instructions) are competitively controlled according to a predetermined priority order, and the instruction (forced occupancy instruction) issued from the host system with the highest priority is selected.
The highest-ranked host system is permitted to access the shared device (external storage device 5), and any commands issued by other host systems (forced occupancy commands) are invalidated, and the shared device is It is configured to notify the identification information (D) of the host system that is permitted to access the device (external storage device 5).

[Effect]

For host systems (1 to 3) that were not granted access rights to the shared device (external storage device 5) due to contention control when the instruction to release the continued occupation state (forced occupation instruction) was issued at the same time. Identification information 10 of the host system to which access rights have been granted is broadcast. Therefore, each host system 1 to 3 can identify whether its own command (forced possession command) or another host system's command (forced possession command) has become valid. Depending on the result, it can be decided whether to reissue the command (compulsory possession order) or to reissue the command (compulsory possession command) as a normal operation. can be prevented.

(Example) The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram showing one embodiment of the present invention, and 1 to 1 are block diagrams showing one embodiment of the present invention.
3 is each host system of the triple system; 4 is an adapter device that allows each host system 1 to 3 to access the external storage device 5; 6 is a status register provided in the adapter device 4; 4 stores identification information 10 of the host system for which the forced occupancy command has been accepted by the adapter device 4 among the forced occupancy commands issued from the host systems 1 to 3, and is transferred to all host systems that have issued the forced occupancy command. be done.

Reference numeral 7 denotes a timer for initializing the contents of the status register 6, and the timer value can be set only by the host system that has received the forced occupancy command by the adapter device 4.

Next, an adapter device with this configuration! ! The operation of step 4 will be explained with reference to the flowchart shown in FIG.

The flowchart in FIG. 2 shows that when the host system 3 is unnecessarily occupying the external storage device 5 due to malfunction or other reasons, a forced occupation command is issued from the host system 1 and 2, and the host system 1 acquires the access right, and the host system 2 waits until the access by the host system 1 is completed.

First, the host system 1.2 sets a timer value in a timer (not shown) for abnormality monitoring during normal operation, and then
When it becomes necessary to access the external storage device 5, an exclusive command is sent to the adapter device 4 (81.82). On the other hand, if the adapter device 4 reports that the host system 3 is already occupying the external storage device 5, check whether the timer for abnormality monitoring has timed up or not. If not, the exclusive command is reissued as a normal operation (83.S4.82).

However, if it is not occupied by another host system, the process immediately moves to accessing the external storage device 5 (S5
).

On the other hand, if the host system 3 occupies the external storage bag @ 5 and the system becomes abnormal due to malfunction or other reasons, the host systems 1 and 2 will be unable to access the external storage device 5 for any length of time. When the abnormality monitoring timers provided inside these host systems 1 and 2 time up, it is recognized that a system abnormality has occurred, and a forced occupancy command is issued as a system recovery means (86.37).

The adapter device 4 that has received this forced occupancy command performs conflict suppression internally according to a predetermined priority order, and forcibly releases the continued state of occupancy of the external storage device [5 by the host system 3 in which the system is abnormal] 88 to S9. ), for example, select a forced occupancy command issued from the host system 1 510),
The host system 1 is caused to transition the occupancy state of the external storage device W15.

At the same time, the identification information ID of the host system that received the forced occupancy instruction is stored in the internal status register 6, and the contents of the status register 6 are reported as status information to the host system 1.2 that issued the forced occupancy instruction. (811). The host systems 1 and 2 that issued the forced occupancy command use this status information to recognize whether the forced occupancy command they issued was successful (312) or whether the one issued by another host system was accepted (813). ). In the example of FIG. 2, the forced occupancy command from the host system 1 has been accepted, so the external storage device 5 shifts to an access state by the host system 1, and the host system 2 waits until the host system 2 completes the access.

Here, the contents of the status register 6 (identification information ID)
is automatically initialized after the set time has elapsed according to the timer value set in timer 7 by the host system 1 that received the forced occupancy command, and before the contents of this register 6 are initialized, the forced occupancy instruction is received from another host system. Even if an instruction is issued, the instruction is invalidated and only the contents of register 6 are reported. Therefore, the host system 1
If the value of the timer 7 is set in accordance with the time for which the host system 2 is desired to be occupied, forced occupation commands from other host systems 2 will be accepted after that time has elapsed.

Note that there are various methods for initializing the contents of the status register 6. For example, there are those that are initialized by the next activation from a host system that has received a forced occupancy command, and those that are initialized by an acknowledgment operation from a host system that has received a forced occupancy command. However, in any case, the subsequent operation from the host system that receives the forced occupancy command must be implicitly guaranteed, and immediately after issuing the forced occupancy command,
If an abnormality occurs in the host system accepted by the adapter device 4, the forced occupancy command from the other host systems will be invalidated because the forced occupancy command has not been completed in the adapter device 4, and the external There is no means of accessing the storage device 5 at all.

In this embodiment, in order to solve the above problem, a timer 7 is provided, and the forced occupancy state is automatically completed after the timer value set in the timer 7 when a forced occupancy command is issued, and the host I try not to make it dependent on the next action from the system.

Therefore, the host system will perform a series of processes after issuing the forced occupancy command within this set time.

Note that the reason why the timer value can be set to an arbitrary value is that the processing after receiving the forced occupancy command differs depending on the preprocessing in which the host system issues the forced occupancy command.

Although the above embodiments have been described with respect to an adapter device for an external storage device, the same effect can be obtained even if the adapter device is a storage device shared by a plurality of host systems or a peripheral device such as a printer device.

Further, in the above embodiment, the explanation was given regarding a forced occupancy command, but the same effect can be expected even with a forced release command. A forced release command, similar to a forced possession command, forcibly releases a shared device such as an external storage device that is occupied by a certain host system. The only difference is that a new exclusive right is granted, whereas a forced release command releases the occupied state, releases the shared device to all host systems, and causes the shared device to be selected for occupation anew. In the case of a forced release command, for example, if host system 1 and host system 2 exchange the command, if the command from host system 1 is accepted, host system 2 will receive the command issued by host system 2. Since it is not reported whether the command was accepted correctly, the host system 2
In this case, the forced release command will be reissued repeatedly, and eventually both host systems 1 and 2 will go down. Therefore, with respect to the forced release command, system failure can be prevented by notifying all host systems of the identification information of the host system that issued the command, which has become valid as in the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, when commands for forcibly releasing a shared device that has been in an occupied state from the continued occupied state are issued at the same time, the issuer host system of the command selected by contention control Since the configuration is configured so that the identification information is notified as status information to all the host systems that have issued the command, it is possible to prevent system down of all the host systems due to the exchange of the command. Furthermore, access by a host system that has acquired access rights can be continued without interruption.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart for explaining the operation of the embodiment, and FIG. 3 is a block diagram of a multi-system system using a conventional adapter device. 1 to 3... host system, 4... adapter device,
5... External storage device, 6... Status register,
7...Timer. Agent Masuo Odai (and 2 others) Figure 1 ¥3

Claims (2)

[Claims] (1) In an adapter device that is attached to a shared device that is commonly accessed by multiple host systems, when a command to forcibly release the shared device from the continuous occupation state is simultaneously issued by multiple host systems, Contention control is performed on the issued instructions according to a predetermined priority order, and the instruction issued from the host system with the highest priority is selected.
Allowing the highest ranking host system to access the shared device, invalidating the command issued from other host systems, and identifying the host system that is permitted to access the shared device. An adapter device configured to broadcast information. (2) The adapter device according to claim 1, wherein the identification information is initialized after a timer time set by the host system that selected the command has elapsed.