JPS61285555A - Computer system - Google Patents

Abstract

PURPOSE:To attain the nonvolatilization of plural journal buffers for a user program of a virtual memory type computer system without the consciousness of a real memory address and the mutual using states among those buffers. CONSTITUTION:A main memory 3 consists of a volatile area and a nonvolatile area 2, and these areas 1 and 2 are divided into real pages respectively. The area 2 includes a control table 6 which contains a user identifier 31 and a using condition flag 32 at every entry. A nonvolatile flag 13 is added to the entry of a real page table and the corresponding flag of the entry corresponding to the area 2 is set ON in a system initialization mode. When an allocation request is given from a user program, the identifier 31 is applied in addition to a virtual page number with a request given to the area 2 in case of a request classification or a nonvolatilization area request thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a new computer system for journaling changes to recoverable objects, including messages, database records, and persistent system state.

[Background of the invention]

In computer systems, databases and system states need to be restored while maintaining their integrity even if the power to the system is cut off due to a failure. To recover from such failures, database management systems (DBMSl) use a journal that stores blocks of C in either main memory buffers and secondary memory, such as disk or magnetic tape.
stored as a collection of records). Data is first written into the buffer and then transferred to the secondary memory IJK when the buffer is full or needs to be permanently stored. In conventional devices, data is written to external secondary memory each time data needs to be retained.The problem is that even if the block size is large, the number of writes occurs frequently in response to write requests from transactions. was there.

On the other hand, according to Japanese Patent Application Laid-Open No. 59-59374, it is possible to make the main memory non-volatile by using a battery, and if a buffer is placed in this main memory, the buffer will not be lost when the power is cut off, and writing can be done without delay. It has the advantage that it only needs to be used when it is full.

However, the table shows that it is impractical from a cost standpoint to power up the entire main memory with a battery, so it would be implemented using partially backed up memory. In a virtual memory computer system, the operating system (O8) collectively performs the association between virtual memory and real memory and the management of real memory.

The database management program outside the O8 (from the O8's point of view, it is seen as the user program -1, henceforth referred to as the user program) processes in virtual memory, so it is necessary to store the buffer in a non-volatile area on the real memory. cannot be assigned.

As a way to deal with this, a method is used in which a certain area of virtual memory is fixedly associated with a non-volatile area of real memory, and allocation is made from virtual memory to a specific part of real memory. , the independence between the user program and the system configuration is lost. Another problem is that it is difficult and undesirable to use a plurality of independent buffers independently of each other from different user programs.

[Purpose of the invention]

An object of the present invention is to make multiple journal buffers of user programs in a virtual memory computer system non-volatile without being aware of real memory addresses and mutual usage status. In addition, if the contents of volatile memory are lost due to a system failure, the user program can be recovered by associating the user program buffer at the virtual address with the same nonvolatile area as before the failure after the system is restarted. The purpose is to enable processing.

[Summary of the invention]

For the above purpose, the present invention employs a method in which the operating system specifically fixes virtual areas requested by user programs to each part of the non-volatile area. At the same time, the operating system sets the user identifier specified by the optical user program in the management table set in the non-volatile area, and determines which data among the data in the non-volatile area is valid after a failure occurs. In addition to ensuring that information is not lost, when a reassignment request is made with the same user identifier as the user program, the corresponding buffer is allocated to the same nonvolatile memory area as before the failure occurred, and the user program Enables access to data in the buffer.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. A conventional computer system includes a main memory 3, an arithmetic control unit 4, and other parts (not shown). The main memory 3 is composed of a volatile area 1 and is divided into pages (C real pages).

On the other hand, the virtual memory is also divided into virtual pages of the same size as the real page and managed by a program (hereinafter referred to as O8) that performs memory management.

To manage real memory, real page table 1 shown in Figure 2 is used.
Use 0. The real page table 10 includes virtual page numbers 11 and 7 lags 12 in use.

The arithmetic control unit 4 includes a virtual address to real address conversion mechanism 5. The correspondence between virtual addresses and real addresses by O8 is performed on a page-by-page basis, and the conversion mechanism 5
The system is notified by setting this correspondence in the 0 page table C (not shown).

A user program makes a request to allocate a real page to a virtual page using a 5vC (supervisor call). At this time, a buffer page number is applied as a parameter.

Allocation by O8 is performed as follows. Find the entry in use with 7 lags off from the real page table,
Turn on the boxing flag, set a virtual page number, and use it as an assigned page. Pages allocated in this way are not subject to paging eviction, and
It will not be released until an SvC of a release request specifying the same virtual page number is made from the user program.

In the present invention, the main memory 3 is composed of a volatile area 1 and a non-volatile area 2, each of which is divided into real pages. The nonvolatile area 2 includes a management table 6.

As shown in FIG. 3, the management table 6 includes a user identifier 31 and a usage status flag 32 for each entry. A non-volatile flag 13 is added to the IJ of the real page table, and the corresponding book of the entry corresponding to the non-volatile area is set to ON at the time of system initialization. When a user program makes an allocation request, in addition to the virtual page number, the requested stock type and if the request type is a non-volatile area request, a user identifier is requested.

FIG. 4 shows the flow of processing at that time. When the request type is non-volatile initial allocation, a search is made for an entry in the management table that has not been updated, and if not, the allocation is determined to be a failure. The found entry is assigned as a real page, a user identifier is set, and it is made available for use. A virtual page number is set in the entry corresponding to the above page in the real page table, and a busy flag is set. When the request type is non-volatile reassignment, the management table is searched for an entry that has the same user identifier as the user identifier of the application, and if it does not exist or the reuse has not started, the assignment is determined to have failed. The found entry is allocated and used as a real page, and the same real page table settings as above are performed. When the request type is volatile allocation, the real page table is searched for an entry that is neither nonvolatile nor in use, and if no entry is found, allocation is determined to have failed. The found entry is assigned as a real page and the real page table is set in the same manner as above. After performing this SvC, the user program performs processing assuming that the contents of the buffer are non-volatile in the event of a power failure.

Finally, the initial setting of the management table at the time of starting the system is performed according to the procedure shown in FIG. It is determined whether it is a restart or not, and if it is not a restart, all entries in the management table are set to an unused state. If restarting, the entries in use are set to reallocation. In this way, the state in which the above-described page allocation process can be performed can be achieved.

〔Effect of the invention〕

According to the present invention, each user program can make its own buffer non-volatile without being aware of the real address. Furthermore, even if the virtual address system has changed after recovery from a system failure, the data before the failure can be accessed via the buffer on the virtual page (using the user identifier).

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the target computer system, Figure 2 is a configuration diagram of a real page table, Figure 3 is a configuration diagram of a management table, and Figure 4 is a diagram of the real page allocation scheme for virtual pages. FIG. 5 is a flowchart of table setting processing at the time of system startup. 1... volatile memory, 2... non-volatile memory, 3...
...Main memory, 4. Arithmetic control unit, 6. Management table, Fig. 4

Claims (1)

[Claims] In a computer system that includes a main memory consisting of a volatile area and a non-volatile area, and an arithmetic control unit whose execution is controlled by virtual addresses and includes an address translation mechanism that converts virtual addresses to real addresses, there is a non-volatile area within the non-volatile area. It has a non-volatile area management table (hereinafter referred to as management table) that stores the usage status of each part and each user identifier as entries.As a function of the program that manages main memory, this management table is stored during initial system setup. It has a function to set all the usage status to unused status or to set the entry in use to start reuse, and when a real area allocation request to a virtual area is requested from another program, the usage application to the non-volatile area is applied. For unaccompanied requests, allocation is made to the volatile area, and for requests for initial use of the non-volatile area, the management table is searched to find and allocate an unused non-volatile area, and as an entry in the management table, In addition to setting the user identifier specified at the time of application, the usage status is set to in use, and for non-volatile area reuse applications, the reuse start area of the management table is searched by the user identifier specified at the time of application. A computer system having a function of reassigning an area having the same user identifier and setting the usage status of a corresponding entry in a management table to be in use.