JP2001067881A - Content addressable storage device and storage medium - Google Patents

Abstract

An object of the present invention is to selectively use an EEPROM and an NVRAM to suppress an increase in the price and prevent an excessive rewriting of the EEPROM, thereby extending the life of the EEPROM. SOLUTION: NVRAM different from EEPROM 13
12 is provided, and hint information on the number of rewrites is input from the user interface unit 14, and the associative array subsystem 1
5 determines whether or not the number of rewrites is large based on the hint information. If the number of rewrites is large, write to the NVRAM 12;
Storage device and storage medium for writing data to a storage device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an associative memory device using an associative array system, and more particularly to an associative memory device and a storage medium which can prevent the life from being shortened due to excessive rewriting and extend the life. .

[0002]

2. Description of the Related Art Conventionally, in computer systems, an associative array system is known in which a headword is provided instead of an address for search, and data is stored in pairs with the headword.

The associative array system is a storage system using an array in which data can be read / written using a character string or the like as a key. This method has the advantage that the key space is very large, but has the disadvantage that there are few (sparse) effective keys. This type of associative array method is, for example, a programming language aw
It is commonly used as k, peal or cache mechanism.

FIG. 7 is a flowchart for explaining a hash type associative array system, and FIG. 8 is a schematic diagram showing a write operation in the associative array system. In this associative array system, a set of a key (key; headword) and values V1 to Vp (data) is stored in the RAM 1 as an associative array. In this associative array method, when a key and a value are input at the time of writing, the key is converted into an array offset by a hash function (ST1), and the value is written to an area in the RAM defined by the array offset. (ST2). As a result, the RAM 1 holds a set of a key and a value combined with the key.

On the other hand, at the time of reading, each area in the RAM 1 is searched based on the input key, and the value linked to the key is read.

An associative memory device using such an associative array system will be described. In the associative storage device, the contents of the associative array are stored in the RAM, and thus disappear when the power is turned off.

However, there are cases where it is desired to preserve the contents of the associative array even after the power is turned off, as in an embedded computer. In this case, the main method is to store the associative array in RAM
There is a method of backing it up to a file with it, and a method of building a database of associative arrays on a file.

In either case, the embedded computer uses an erasable ROM (hereinafter, referred to as a ROM) having a limit on the number of rewrites.
A file system using an EEPROM is mainly used.

[0009]

However, in the associative memory device described above, when the database is frequently rewritten, the number of times of rewriting the EEPROM becomes excessive,
Since the number of times of rewriting of the EPROM is limited, the life of the database is shortened.

On the other hand, from the viewpoint of creating a database capable of storing data even after the power is turned off without excessively rewriting the EEPROM, a battery-backed RAM (hereinafter referred to as N
It is conceivable to use VRAM (referred to as non-volatile RAM). However, NVRAM has few vendors and is expensive, so it is difficult to construct a large database.

The present invention has been made in consideration of the above circumstances, and has a structure in which an EEPROM and an NVRAM are selectively used, thereby suppressing an increase in the price and preventing an excessive rewrite of the EEPROM to extend the life. It is an object of the present invention to provide an associative storage device and a storage medium that can be obtained.

[0012]

According to a first aspect of the present invention, an associative array is constructed on a RAM, and EEP is written at the time of writing.
What is claimed is: 1. An associative memory device capable of executing associative memory on a ROM, which is different from the EEPROM in that the nonvolatile memory means has no limit on the number of rewrites, and the hint information input means inputs hint information on the number of rewrites. Determining whether or not the number of rewrites is large based on the hint information input by the hint information input means, writing the nonvolatile storage means when the number of rewrites is large, and The content addressable memory device includes a writing unit that writes data to the EEPROM.

According to a second aspect of the present invention, in the associative memory device according to the first aspect, when the nonvolatile storage means is full, a predetermined amount of data in the nonvolatile storage means is stored in the EEPROM. It is an associative storage device provided with a data moving means for moving.

According to a third aspect of the present invention, in the content addressable storage device according to the second aspect, the data moving means stores the data in the chronological order of the last rewriting time from the oldest one.
This is an associative storage device that is moved to an EPROM.

According to a fourth aspect of the present invention, an associative array is constructed on a RAM, and the associative memory can be executed in an EEPROM at the time of writing.
A computer-readable storage medium used for an associative storage device having a non-volatile storage unit that has no limitation on the number of rewrites unlike the computer of the associative storage device. When the number of rewrites is large, it is determined whether the number of rewrites is large based on the hint information. When the number of rewrites is large, writing is performed on the non-volatile storage means, and when the number of rewrites is small, writing is performed on the EEPROM. It is a computer-readable storage medium that stores a program for causing it to function as a writing unit.

Further, according to a fifth aspect of the present invention, in the computer readable storage medium according to the fourth aspect, the computer of the associative storage device stores the non-volatile storage when the non-volatile storage is full. A computer-readable storage medium storing a program for causing a predetermined amount of data in the means to function as data moving means for moving the data to the EEPROM.

According to a sixth aspect of the present invention, in the computer readable storage medium according to the fifth aspect, a program for moving data to the EEPROM in an order of oldest last rewriting time as the data moving means. Is a computer-readable storage medium having stored therein.

(Operation) Accordingly, the invention corresponding to the first and fourth aspects has the above-described means, and thus the EEPR
Unlike the OM, a non-volatile storage unit having no limit on the number of rewrites is provided, the hint information input unit inputs hint information on the number of rewrites, and the writing unit sets the hint information based on the hint information input by the hint information input unit. To determine whether the number of rewrites is large. If the number of rewrites is large, write to the non-volatile storage means.
Since data is written to M, the EEPROM and the NVRAM are selectively used.
Excessive rewriting of the OM can be prevented to extend the life.

According to a second aspect of the present invention, when the non-volatile storage means is full, the data moving means moves a predetermined amount of data in the non-volatile storage means to the EEPROM. In addition to the actions corresponding to 1, 4
The writing process can be continued even when the non-volatile storage means is full.

Further, the invention corresponding to claims 3 and 6 is:
Since the data moving means moves the data to the EEPROM in the order of the oldest rewriting time, the action corresponding to the first and fourth aspects can be achieved easily and reliably.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a configuration of an associative memory device according to a first embodiment of the present invention. The associative storage device 10 includes a RAM 11, an NVRAM 12, an EE
It includes a PROM 13, a user interface unit 14, an associative array subsystem 15, and a queue 16.

Here, the RAM 11 stores an associative array so that the associative array can be read / written by the associative array subsystem 15. As shown in FIG. 2, the associative array includes at least four elements: a key, a value linked to the key, a pointer indicating an area on the EEPROM 13, and a pointer indicating an area on the NVRAM 12.

The NVRAM 12 is a nonvolatile memory having a battery backup and has an unlimited number of rewrites. The associative array is stored in the associative array subsystem 15 in a readable / writable manner.

The EEPROM 13 is non-volatile and has a limit on the number of rewrites. The associative array is stored in the associative array subsystem 15 in a readable / writable manner.

The user interface unit 14 inputs and outputs data between a user (or another computer) and the inside of the associative storage device 10. For example, a keyboard as an input device and a display device as an output device ( Or an interface to another computer).

The associative array subsystem 15 operates according to a program read from a storage medium (not shown).
U, which performs reading from the RAM 11 based on a reading request from the user interface unit 14,
It has a function of executing writing to the EEPROM 13 or the NVRAM 12 based on a write request from the user interface unit 14 and hint information. The hint information is EE
This is information for selecting either the PROM 13 or the NVRAM 12, and includes, for example, “many rewrites” when the number of rewrites is expected to be large.

The associative array subsystem 15 has an EE
Using the queue 16 in the writing process to the PROM 13,
The value stored first in the queue 16 together with the key in the EEPR
It has a function of writing to the OM 13 and a function of issuing the next write request and storing it in the queue 16 every time the writing is completed. The queue 16 is a write queue constituted by a storage area having a first-in first-out (FIFO) property, and can be formed in, for example, the RAM 11 in a different area from the associative array storage area.

Next, the operation of the associative memory configured as described above will be described. It is assumed that the user interface unit 14 has input a read request specifying a key to the associative array subsystem 15 by an operation of the operator.

The associative array subsystem 15 returns a value corresponding to a key in the associative array of the RAM 11 in response to the read request. Thus, the read operation of the content addressable memory device 10 is completed.

Next, the write operation will be described. Now, it is assumed that the user interface unit 14 inputs a write request specifying a pair of a key and a value and hint information to the associative array subsystem 15 by an operation of the operator.

The associative array subsystem 15 writes a value to the memory area corresponding to the key in the same manner as in steps ST1 and ST2 described above. However, unlike the conventional case, in step ST2, either the NVRAM 12 or the EEPROM 13 is selected. .

That is, the associative array subsystem 15
As shown in FIG. 3, in response to a write request, it is determined whether or not the number of rewrites is large based on hint information (ST11). If the number of rewrites is large, an attempt is made to secure a storage area of the NVRAM 12 (ST12). , When the storage area can be secured, N
The key and the value are written to the VRAM 12 (ST13).

When the associative array subsystem 15 finds that the number of rewrites is small as a result of step ST11, or when the storage area of the NVRAM 12 cannot be ensured in step ST12, it attempts to secure the storage area of the EEPROM 13 (ST14). If the storage area cannot be secured, an error is output (ST15) and the process ends.
When the storage area is secured, the key and the value are written to the EEPROM 13 (ST16).

Here, the process of writing to the EEPROM 13 will be described with reference to FIG. Associative array subsystem 1
5 judges whether or not the first write request of the queue 16 can be executed (ST16a). If the request cannot be executed, the process waits for a predetermined time and re-executes step ST16a. Is written (ST16b).

Subsequently, step ST16b or ST13
After completion of the writing by the associative array subsystem 15, the RA
Write an associative array to M11. As described above, according to the present embodiment, the NVRAM 12 is provided, hint information on the number of rewrites is input from the user interface unit 14, and the associative array subsystem 15 determines whether the number of rewrites is large based on the hint information. If the number of rewrites is large, N
Writing to the VRAM 12 is performed, and when the number of times of rewriting is small, writing to the EEPROM 13 is performed.

As described above, by selectively using the EEPROM 13 which is appropriate in price but has a limited number of rewrites and the NVRAM 12 which is expensive but has no limit in the number of rewrites, the contents can be saved even when the power is turned off. In addition, it is possible to extend the life of the EEPROM 13 by preventing excessive rewriting of the EEPROM 13 while suppressing an increase in price.

EEPR, which is much slower than RAM 11
By using the associative array without accessing the OM 13 every time, the speed can be increased. In addition, EEPROM
The RAM 11 and the NVRAM 12 can be accessed even while the data 13 is being written.

The EEPROM 13 or the NVRAM 1
After the writing of No. 2 is completed, the data in the RAM 11 is rewritten, so that the unwritten data can be treated as “data before rewriting”. Further, since the associative array subsystem 15 performs the above operation, even an operator who is not interested in the internal structure can handle it.

(Second Embodiment) FIG. 5 is a block diagram showing a configuration of an associative memory device according to a second embodiment of the present invention. The same parts as those in FIG. The description will be omitted, and only different portions will be described here. That is, the present embodiment is a modification of the first embodiment, and aims at smoothing the operation when the NVRAM 12 is full. Specifically, the last rewriting time is added to the associative array, and NVRA is executed based on the last rewriting time.
When M12 is full, LRU (Least Recently Recently) transfers a predetermined amount of data in NVRAM 12 to EEPROM 13.
Used: the longest unused) processing unit 17 is provided.

As shown in FIG. 6, the associative array in the RAM 11 has an element called last rewrite time added to the above four elements.

Here, the LRU processing unit 17 uses a known LRU algorithm effective for local access, and moves to the EEPROM 13 in order from the data having the oldest last rewriting time based on the last rewriting time. It has the function to make it. This movement function is performed by the EEPROM 13
Alternatively, priority is given to selection based on “hint information” for selecting the NVRAM 12. That is, when the NVRAM 12 is full, even if the NVRAM 12 is selected, the NVR
Before writing to AM12, the data in NVRAM12 is
Move to EPRAM13.

According to the above-described configuration, when the NVRAM 12 is full, the LRU processing unit 17
A predetermined amount of data in 12 is moved to EEPROM 13. Therefore, when the capacity of the NVRAM 12 is exceeded by rewriting, the rewriting of the EEPROM 13 increases, but the possibility of falling into a “service stoppage when full” state is reduced, and the writing process can be continued. In addition, it is possible to optimize the arrangement according to the access frequency, and to achieve high-speed access.

(Third Embodiment) Next, an associative storage device according to a third embodiment of the present invention will be described. The associative array may not be constructed only by software but may be constructed by hardware. More specifically, in the present embodiment, the EEPROM 13 or the NVRA
M12 is specified and pasted in units of virtual pages. Each virtual page uses a general bit indicating that writing has been completed for the LRU, and whether or not writing has been performed can be referred to. Therefore, according to the above-described configuration, the real memory for the virtual page can be replaced based on the pasting content specified in advance, so that the content can be saved even when the power is turned off, as in the first embodiment. In addition, it is possible to prevent the EEPROM from being excessively rewritten and prolong the life thereof while suppressing the increase in the price.

The storage medium in the present invention includes a magnetic disk, a floppy (registered trademark) disk, a hard disk, and an optical disk (CD-ROM, CD-R, DV).
D (registered trademark)), a magneto-optical disk (MO or the like), a semiconductor memory, or any other storage medium that can store programs and that can be read by a computer.

An OS (Operating System) running on the computer based on instructions of a program installed in the computer from the storage medium,
MW for database management software, network software, etc.
(Middleware) or the like may execute a part of each process for realizing the present embodiment.

Further, the storage medium of the present invention is not limited to a medium independent of a computer, but also includes a storage medium in which a program transmitted via a LAN, the Internet, or the like is downloaded and stored or temporarily stored.

Further, the number of storage media is not limited to one, and the case where the processing in the present embodiment is executed from a plurality of media is also included in the storage medium of the present invention, and any media configuration may be used.

The computer according to the present invention executes each processing in the present embodiment based on a program stored in a storage medium. An apparatus such as a personal computer and a plurality of apparatuses are connected to a network. Any configuration such as a system described above may be used.

The computer in the present invention is
It is not limited to a personal computer, but also includes a processing device, a microcomputer, and the like included in an information processing device, and generically refers to a device and a device capable of implementing the functions of the present invention by a program.

In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0051]

As described above, according to the present invention, E
With the configuration in which the EPROM and the NVRAM are selectively used, it is possible to provide an associative storage device and a storage medium that can prevent the EEPROM from being overwritten and extend the life thereof while suppressing an increase in price.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an associative storage device according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram showing an associative array in a RAM according to the embodiment;

FIG. 3 is a flowchart for explaining a write operation in the embodiment;

FIG. 4 is a flowchart for explaining a write operation in the embodiment;

FIG. 5 is a block diagram illustrating a configuration of an associative storage device according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing an associative array in a RAM according to the embodiment;

FIG. 7 is a flowchart for explaining a conventional associative array method.

FIG. 8 is a schematic diagram showing a write operation in a conventional associative array system.

[Explanation of symbols]

 10, 10a: associative storage device 11: RAM 12, NVRAM 13, EEPROM 14, user interface unit 15, associative array subsystem 16, queue 17, LRU processing unit

Claims (6)

[Claims] 1. An associative memory device capable of constructing an associative array on a RAM and executing associative storage in an EEPROM at the time of writing, wherein the nonvolatile memory has no limit on the number of rewrites unlike the EEPROM. Storage means; hint information input means for inputting hint information relating to the number of rewrites; and determining whether or not the number of rewrites is large based on the hint information input by the hint information input means; Writing means for writing to the non-volatile storage means at times, and writing to the EEPROM when the number of times of rewriting is small is provided. 2. The associative storage device according to claim 1, further comprising: a data moving unit that moves a predetermined amount of data in the nonvolatile storage unit to the EEPROM when the nonvolatile storage unit is full. An associative memory device characterized by the above-mentioned. 3. The associative memory device according to claim 2, wherein said data moving means moves the data to said EEPROM in the order of older last rewriting time. 4. An associative array is constructed on a RAM, and associative memory can be executed on an EEPROM at the time of writing.
And a computer-readable storage medium used for an associative storage device provided with a nonvolatile storage unit having an unlimited number of rewrites unlike the EEPROM, wherein a computer of the associative storage device is provided with hint information on the number of rewrites. Is input, it is determined whether or not the number of rewrites is large based on the hint information. When the number of rewrites is large, writing is performed in the nonvolatile storage means. When the number of rewrites is small, the EEPRO
A computer-readable storage medium storing a program for causing M to function as a writing unit that writes to M. 5. The computer-readable storage medium according to claim 4, wherein the computer of the associative storage device stores a predetermined amount of data in the nonvolatile storage unit when the nonvolatile storage unit is full. A computer-readable storage medium on which a program for functioning as a data transfer means for transferring data to an EEPROM is recorded. 6. The computer-readable storage medium according to claim 5, wherein the data transfer means stores a program for moving data to the EEPROM in the order of oldest last rewriting time. .