JPS6010359A - Skip reading system of record in sequentially edited file - Google Patents

Abstract

PURPOSE:To attain the efficient utilization of main storage by providing a sequentially edited file having a record managing record to which information representing the name and size of each record in the order of storage is stored relating to each record and a file access device referencing in order a content of said record managing record and conducting reading or read skip processing. CONSTITUTION:A block is read from an external storage device 1 to an input buffer 2 by a file access device 5. The file access device 5 observes information relating to a record and conducts reading or skip reading. Thus, a head record 4H and a record managing record 4R are provided before a head record 4-1 in the sequential file structure. Various file information is stored in the 4H and the information representing the name and size of each record in the order of storage relating to each record from next is stored in the 4R.

Description

DETAILED DESCRIPTION OF THE INVENTION When reading a sequential file composed of variable-length records, the present invention refers to record management records to read records that are unnecessary to the user and skip records that are necessary. The present invention relates to a method for skipping records in a sequential file.

[Conventional technology and problems]

FIG. 1 is a diagram illustrating a method of skipping records in a conventional sequential file, and FIG. 2 is a diagram showing an example of the structure of a variable-length record sequential file. In the figure, 1 is an external storage device, 2 is an input buffer, 3 is a buffer area,
4-1 to 4-3 indicate records.

File organizations that can be processed by C0BOL programs include 1-dimensional files using sequential data pipe sets, relative files using keyless direct data sets, direct files using single-key direct data sets, and VS files. A M (Virtual Storage
Access Method) There are VSAM files that use data e-sets, etc. The sequential data φ set is
Create a block by grouping any number of records that are the processing unit of the user program.

This is a data Φ set written on a recording medium in the order in which it occurs, and various input/output devices can be selected as the storage medium, but the user can program the program using unified macro instructions without being aware of the differences in control over each device. can be written. Record formats include fixed length format, variable length format, indefinite length format, and data format.

Conventionally, when reading necessary records into a buffer area on the user side from a sequential file consisting of variable length records, a user program issues, for example, a GET command. As a result, as shown in FIG. 1, the file access mechanism reads blocks from the external storage device 1 (sequential file) into the input buffer 2,
The code is read into the buffer area 3 on the user side one by one from the big sword B7A2, and necessary records are read and unnecessary records are skipped. kot'L#-I
l', variable length records, so even if an unnecessary record is to be skipped, information such as the size of the record to be skipped is not known. Therefore, for example, when reading record 4-3 of a sequential file consisting of records 4-1 to 4-3 as shown in Figure 2, record 4-2 is an unnecessary record and will be skipped. Since it is necessary to read the record 4-2 once into the buffer area 3, a buffer area Fi in the record length of this record 4-2 must be prepared in advance.

In this way, the user must always prepare a buffer area in advance for the length of the largest record in the file, which means that there is a large loss in space when such large records are not needed. It will also force you.

[Purpose of the invention]

The present invention is based on the above considerations.

The purpose of this invention is to provide a method for skipping records in a sequential file, which requires only a buffer area on the reading side in the length of the record and enables efficient use of main memory.

[Structure of the invention]

For this reason, the method of skipping records in sequential files of the present invention is applicable to sequential files with variable length records,
A file 9 access mechanism includes a manual buffer from which blocks of the sequential file are read by the file ψ access mechanism, and a buffer area on the user side for reading records, from the sequential file to the buffer area through the manual buffer. This is a record skipping method in a sequential file that skips unnecessary records when reading records. The file access mechanism has a stored record management record, and the file access mechanism is configured to hold the record management record, sequentially refer to the contents of the record management record, and perform read or skip processing of the record. It is characterized by being embroidered.

[Embodiments of the invention]

Below is one shot ψ” real jf! ill will be explained with reference to the drawings.

FIG. 3 is a diagram explaining one embodiment of the present invention, FIG. 4 is a diagram showing one embodiment of a file structure to which the present invention is applied, and FIG.
The figure is a diagram illustrating an example of record reading and skipping processing. In the figure, J is an external storage device, 2 is an input buffer, 3 is a buffer area, 4-1 to 4-5 are records, 4H is a record management record, and 4R is a record management record.

Reference numeral 5 indicates a file access mechanism, 6 indicates a user-written program, and 7 indicates a variable-length record sequential file.

The present invention enables a user to read unnecessary records into his or her own program area without actually reading them into his or her own area, when a user reads a II-organized file containing variable-length records into his or her own program area. This is to make it possible.

In that case, as shown in Figure 3, %GET 5KIP
When such an instruction is issued, it is skipped in the file access mechanism 5 without being read into the buffer area 3, which is the user's program area.

That is, in FIG.
The access mechanism 5 reads the block into the input buffer 2. Here, the file 9 access mechanism looks at the information regarding the record, reads it, and performs skipping.

Second, in the structure of the sequential file, as shown in FIG. 4, a hand record 4H and a record management record 4R are provided before the first record 4-1. The head Φ record 4H stores various types of file information, including information indicating the size of the next record management record 6. Record management record 4
R stores information indicating the name and size of each record in the order in which it is stored. The file access mechanism 5 accesses this record management record 4R.
By holding , records can be read or skipped while being referenced in order. Further, by looking at the record management record 4R, the user can also know in advance the name and size of the record that he or she needs.

For example, Figure 5 shows an example of reading the second and third records, skipping the fourth record of the first, and then reading the fifth record.
In the figure, a file access mechanism 5 is shown.

Hold the record management record 4R, read records 4-2 and 4-3 according to the GES DATA command of the user's own progera L 6, skip record 4-4 according to the GET 5KIP command, and read the next GETDATA.
Read records 4-5 according to the command.

〔Effect of the invention〕

As is clear from the above description, one aspect of the present invention is that the area size of the buffer to be prepared on the reading side is the maximum record length among the records required on the reading side, and unnecessary There is no need to prepare a large buffer area. Therefore, it becomes possible to use the raw memory efficiently.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the record skipping method in a conventional sequential seven-aisle system, FIG. 2 is a diagram showing an example of the structure of a variable-length record sequential file, and FIG. 3 is a diagram explaining one embodiment of the present invention. 4A and 4B are diagrams showing an example of a file structure to which the present invention is applied, and FIG. 5 is a diagram illustrating an example of processing for reading and skipping records. 1...External storage device, 2...Input buffer, 3...
・Buffer area, 4-1 to 4-5...record,
4H...Head record, 4R...Record management record, 5...File sound access mechanism, 6...
User program, 7...Variable length record sequential organization 7
Aino' 0 hole 1 flash 23 figure

Claims (1)

[Claims] a sequential file with variable length records; a file access mechanism, an input buffer into which blocks of the sequential file are read by the file access mechanism; and a buffer area on the user side from which records are read; A record skipping method in a sequential file that skips unnecessary records when reading records into the buffer area through a manual buffer, the sequential file has the following steps:
It has a record management record in which the name of each record and information indicating thick@埒are stored in the order in which each record is stored,
Records in a sequential file, characterized in that the file access mechanism is configured to hold the record management record, sequentially refer to the contents of the record management record, and perform record read or skip processing. The reading skip method.