JPS60224178A - Accessing system of indexing order forming file using disk cash - Google Patents

Abstract

PURPOSE:To increase the accessing efficiency of an indexing order forming file, by storing index sections in different locations at every external recording media when the indexing order forming file is created. CONSTITUTION:When a indexing order forming file is newly created to an external recording medium 2, index sections Ia'-In' of the medium 2 are respectively stored in different blocks, such as B0, B1,-Bk, Bk+1. When a host device accesses the index section Ia' to fetch the content of Da', for example, a block Da'1, the index section Ia' is stored in the sets S0 and S1 of the level L0 of a disk cash 3 by means of an external storage controller. When the external storage controller is accessed thereafter to fetch the Da'1, necessary data are read from a recording medium 2a and sent to the host device. When the index section Ib' is accessed, the index section Ib' is stored in the sets S2 and S3 of the level L0 of the disk cash 3 correspondingly to the blocks B2 and B3. Since no overlay storage of the index section to the disk case 3 is made, the accessing efficiency is improved.

Description

Detailed Description of the Invention (Technical Field) The present invention provides an index order method using a disk cache that uses a disk cache to access an index order organization file consisting of a plurality of external storage media each having an index section. Concerning access methods for organizational files.

(Prior art) Conventionally, when a disk cache is used for this type of indexed sequential file, the index section for each external storage medium is mapped to the same location in the disk cache, so the frequently accessed index section is not stored in the disk cache. The disadvantage is that it cannot be made permanent. This will be explained using drawings.

FIG. 1 is a block diagram showing the configuration of a method for accessing index sequential files using a disk cache.

1st: The access method shown in the figure is an external storage device 1, an external storage medium 2 which is composed of a magnetic disk and stores indexed files, a disk cache 3, and an external storage device according to an access request from a host device. 1, an external storage control device 4 that controls the disk cache 3 and retrieves necessary data;

FIG. 2 shows a data storage diagram of the conventional access method. Hereinafter, when the external storage medium 2 is referred to, it refers to the entire external storage medium. Information is recorded on the external storage medium 2 for each block B0°B, . . . which is a physical access unit. Here, the structure of the index sequential file of the external storage medium 2 is block B0. Index section construction a consists of two blocks: and B.

. . . Ik, . . In, and a plurality of blocks of data portion Da.

Db,...pn are getting worse.

The disk cache 3 shown in FIG. Consisting of memories, one level in the set (e.g. 8o-level LD) has a capacity equivalent to a block (e.g. B6) of the external storage medium 2.

Now, with the disk cache 3 in its initial state, data D on the external storage medium 2a is sent from the host device to the external storage control device 4.
Assume that index section Ia is accessed to retrieve at. Since the disk cache 3 is in the initial state, the external storage control device 4 reads data from the external storage medium 2a four times and stores the data in the disk cache 3. As shown in FIG. 2-), the index portion Ia of the external storage medium 2a is first stored in cells 8o and S at level L0. Subsequently, the data Da1 is accessed from the host device, and the external storage control device 4 reads the external storage medium 2a. The read data is not stored in the disk cache L3, but is sent directly to the host device.

That is, the external storage control device 4 is the index section Ia.

The contents of the disk cache 3 are checked only when access to Ib, . . .
The data is read and stored in the disk cache 3. In addition, each block of the external storage medium 2 is stored in the disk cache 3 (cellar) 80. S, ... respectively, and when the maximum number of sets is exceeded, the next level is s, t.
External storage control device 4 so as to be associated with 81t...
controlled by Note that the contents of parentheses at each level within the set of the disk cache 3 indicate the external storage medium in which data is stored and the corresponding block.

Next, the data on the external storage medium 2b is transferred from the host device to the external storage medium 2b.
When the index section 1b is accessed to retrieve the data, the external storage control device 4 stores the index section I in the disk cache 3.
Since there is no data in b, data is read from the external storage medium 2b. and block B of the external storage medium 2b,
, B is attempted to be stored in the set S0, 8m of the level L0, but since the information has already been stored, it is stored in the empty set S, , Sl of the Vpel L.

After the above-mentioned access from the host device is performed multiple times to different external storage media 2 and the index part is stored up to the disk cache 30 level Lj-1, access is made to another external storage medium 2. When φ access is requested,
In other words, the number of external storage media 2 is the disk cache JL3.
When the number of levels j is exceeded, the external storage control device 4 performs overlay storage in the disk cache 3.

This applies to each level L0 within the set. L,...I,
Among the contents of j-l, overlay storage is performed on the level that was accessed the oldest in terms of time. Currently level L
Assuming that 0 meets that condition, the final storage state of the disk cache 3 will be as shown in FIG. 2(C).

As is clear from the above explanation, when the number of levels of the disk cache 3 (j in this example) is smaller than the number of external storage media 2, overlay storage of the disk cache 3 will be performed frequently. The index cannot be made resident in the disk cache Lt. This results in an extremely large drop in access efficiency when the file is organized in index order. That is, index parts Ia, Ib, which are always accessed,
... is often not on the disk drive 33,
This is because physical access to the external storage medium 2 is frequently performed.

As described above, the conventional indexed sequential file access method using a disk cache has the drawback of significantly reducing access efficiency.

(Objective of the Invention) An object of the present invention is to use a disk cache, which greatly increases access efficiency compared to conventional methods, by storing the index part in a different location for each external storage medium when creating an index sequential file. The purpose of this invention is to provide an access method for indexed sequential files.

(Structure of the Invention) The method of the present invention includes: an index sequential file composed of a plurality of external storage media in which index portions are stored in different storage positions for each external storage medium; a disk cache in which information is stored; When an access request is made to the index section of the index sequential file, the necessary information is read from the corresponding external storage medium using the index section stored in the disk cache, stored in the disk cache, and then sent to the index section. When an access request is made, the index section stored in the corresponding external storage medium of the index sequential file is read out and the set of the disk cache corresponding to the storage block of the external storage medium in which the index section is stored is read out. It is configured to include reading and storing means for storing.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a data storage diagram of one embodiment of the present invention.

FIG. 3(a) shows the storage state of index sequential files in the external storage medium 2 of the external storage medium 1.

Ial, from /, . . . In / indicates the index section of the index sequential file, and Da', Db', . . . p n I indicate the data section of the index sequential file.

As shown in FIG. 3 (11), when creating a new index sequential organization file in the external storage medium 2, the index sections a', lb', ... n' of the external storage medium 2 are Store it so that it is located in a different block. Taking the external storage medium 2b as an example, the index section Ib/ is stored in the block B, B, which is a different block from the block B, B, in which the index section a' of the external storage medium 2a is stored. The data portion Db' is stored after block B4.

In the above state, when the host device accesses the index section J a / to retrieve the contents of the diblock Da', for example, the block Dat', the external storage control device 4
First, index section a' is at level L of disk cache 3. ) 8o, stored in Sl. Next, when the corresponding block 1)at' is accessed by the external storage control device 4, the required data is read from the external storage medium 2a and sent to the host device. Furthermore, the index sIb' for higher-level devices
When there is an access to the block B, the index section Ib' is controlled by the external storage control device 4 to
Guisuku Cash: L30 level L6. Set S! and stored in Sl.

As described above, in this embodiment, when the external storage control device 4 is accessed by the host device, the index portions Ia', lb', .
...In2 will not be stored redundantly on the disk cache 3.

(Effects of the Invention) The present invention enables overlay storage of the index part in the disk cache by storing the index part in different storage locations in the external storage medium when creating the index sequential file. The lost index section can be made resident in the disk cache, which has the effect of greatly improving access efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram H2E(a) showing the configuration of a data access method using a disk cache. 3(b) and (e) are data storage diagrams of the conventional data access method, and FIG. 3(a), φ) 9- is a data storage diagram of an embodiment of the present invention. 1...External storage device% 212al 2b?・
2n... External storage medium, 3... Disk cache, 4... External storage control device.

Claims (1)

[Scope of Claims] An index sequential organization file consisting of a plurality of external storage media in which index portions are stored in mutually different storage positions for each external storage medium, a disk cache for storing information, and the index sequential organization file. When a request is made to access an index section, the required information is read from the corresponding external storage medium using the index section that is stored in the disk cache.When a request is made to access an index section that is not stored in the disk cache, the necessary information is read out from the corresponding external storage medium using the index section that is stored in the disk cache. Reading out an index section stored in a corresponding external storage medium of an index organization file and storing it in the set of the disk cache corresponding to the storage block of the external storage medium in which the index section is stored. An indexed sequential file access method using a disk cache, comprising: