Dataset

[Former Member]

Hi,

anyone can explain me what are datasets and what are they meant for .

what are open dataset, read dataset, close dataset.

[Former Member]

datasets are the file son the application server.

open dataset opens the file for reading / writing or appending records.

read dataset reads the data from teh file to the work area / variables of the program

close dataset closes the file on the application server.

Regards,

Ravi

[former_member673464]

hi,

OPEN DATASET dset FOR access IN mode [position]

[ os_addition]

[error_handling].

Effect

This statement opens the file specified in dset for the access specified in access in a storage mode specified in mode. For dset, a character-type data object is expected, which contains the platform-specific name of the file.

Use additions position, os_addition and error_handling to determine the position at which to open the file, to specify platform-specific additions and to influence error handling.

In Unicode programs, the access and storage modes access and mode must be specified explicitly. If the additions are missing in non-Unicode programs, the file is opened implicitly as a binary file for read access.

In Unicode programs, the file must not yet be open in the current program; otherwise a treatable exception occurs. In non-Unicode programs, the file may already be open. The statement OPEN DATASET then does not reopen the file but moves the read or write position depending on the access mode. In this case, you should not change the access or storage mode.

READ DATASET dset INTO dobj [MAXIMUM LENGTH mlen]

[[ACTUAL] LENGTH alen].

Extras:

1. ... MAXIMUM LENGTH mlen

2. ... [ACTUAL] LENGTH alen

Effect

This statement exports data from the file specified in dset into the data object dobj. For dobj, variables with elementary data types and flat structures can be specified. In Unicode programs, dobj must be character-type if the file was opened as a text file.

For dset, a character-type data object is expected - that is, an object that contains the platform-specific name of the file. The content is read from the file starting from the current file pointer. After the data transfer, the file pointer is positioned after the section that was read. Using the MAXIMUM LENGTH addition, the number of characters or bytes to be read from the file can be limited. Using ACTUAL LENGTH, the number of characters or bytes actually used can be determined.

In a Unicode program, the file must be opened with an arbitrary access type; otherwise, an exception that cannot be handled will be triggered.

CLOSE DATASET dset.

Effect

This statement closes the file specified in dset. dset must be character-type data object that contains the platform-specific name of the file. If the file is already closed or does not exist, the statement is ignored and the return value sy-subrc is set to 0.

If the operating system buffers data before it is written to a file and there is still data in the buffer, this data is written to the file before closing.

Note

An opened file that was not explicitly closed using CLOSE DATASET is automatically closed when the program is exited.

System fields

If a file was opened without the FILTER addition, sy-subrc always contains the value 0.

If a file was opened using the FILTER addition, sy-subrc contains the return value of the filter program, which is returned by the operating system. This value is generally 0 if the statement was executed successfully.

regards,

veeresh

[Former Member]

hi,

Open Dataset is used to read or write on to application server ... other than that i am not sure that there exists any way to do the same ... here is a short description for that

FILE HANDLING IN SAP

Introduction

• Files on application server are sequential files.

• Files on presentation server / workstation are local files.

• A sequential file is also called a dataset.

Handling of Sequential file

Three steps are involved in sequential file handling

• OPEN

• PROCESS

• CLOSE

Here processing of file can be READING a file or WRITING on to a file.

OPEN FILE

Before data can be processed, a file needs to be opened.

After processing file is closed.

Syntax:

OPEN DATASET <file name> FOR {OUTPUT/INPUT/APPENDING}

IN {TEXT/BINARY} MODE

This statement returns SY_SUBRC as 0 for successful opening of file or 8, if unsuccessful.

OUTPUT: Opens the file for writing. If the dataset already exists, this will place the cursor at the start of the dataset,

the old contents get deleted at the end of the program or when the CLOSE DATASET is encountered.

INPUT: Opens a file for READ and places the cursor at the beginning of the file.

FOR APPENDING: Opens the file for writing and places the cursor at the end of file. If the file does not exist, it is generated.

BINARY MODE: The READ or TRANSFER will be character wise. Each time ‘n’’ characters are READ or transferred.

The next READ or TRANSFER will start from the next character position and not on the next line.

IN TEXT MODE: The READ or TRANSFER will start at the beginning of a new line each time.

If for READ, the destination is shorter than the source, it gets truncated.

If destination is longer, then it is padded with spaces.

Defaults: If nothing is mentioned, then defaults are FOR INPUT and in BINARY MODE.

PROCESS FILE:

Processing a file involves READing the file or Writing on to file TRANSFER.

TRANSFER Statement

Syntax:

TRANSFER <field> TO <file name>.

<Field> can also be a field string / work area / DDIC structure.

Each transfer statement writes a statement to the dataset. In binary mode, it writes the length of the field to the dataset.

In text mode, it writes one line to the dataset.

If the file is not already open, TRANSFER tries to OPEN file FOR OUTPUT (IN BINARY MODE) or using the last OPEN DATASET statement for this file.

IF FILE HANDLING, TRANSFER IS THE ONLY STATEMENT WHICH DOES NOT RETURN SY-SUBRC

READ Statement

Syntax:

READ DATASET <file name> INTO <field>.

<Field> can also be a field string / work area / DDIC structure.

Each READ will get one record from the dataset.

In binary mode it reads the length of the field and in text mode it reads each line.

CLOSE FILE:

The program will close all sequential files, which are open at the end of the program.

However, it is a good programming practice to explicitly close all the datasets that were opened.

Syntax:

CLOSE DATASET <file name>.

SY-SUBRC will be set to 0 or 8 depending on whether the CLOSE is successful or not.

DELETE FILE:

A dataset can be deleted.

Syntax:

DELETE DATASET <file name>.

SY-SUBRC will be set to 0 or 8 depending on whether the DELETE is successful or not.

Pseudo logic for processing the sequential files:

For reading:

Open dataset for input in a particular mode.

Start DO loop.

Read dataset into a field.

If READ is not successful.

Exit the loop.

Endif.

Do relevant processing for that record.

End the do loop.

Close the dataset.

For writing:

Open dataset for output / Appending in a particular mode.

Populate the field that is to be transferred.

TRANSFER the filed to a dataset.

Close the dataset.

Regards

Reshma

[Former Member]

OPEN DATASET is for opening a file on Application server.

READ DATASET is for opening a file on Application server. the purpose could be for reading or writing.

CLOSE DATASET is for closing a file opened.

Just press F1 on DATASET for more details like syntax etc...

Reward points if useful

Regards