topic Re: what is open data set and close data set in Application Development and Automation Discussions

what is open data set and close data set

Former Member — Sat, 11 Nov 2006 08:08:26 GMT

what is open data set and close data set,

how to use the files in sap directories ?

Re: what is open data set and close data set

Former Member — Sat, 11 Nov 2006 08:22:14 GMT

OPEN DATASET stmt is used to open a file on applicaiton server either for reading or writing.

Eg: OPEN DATASET <dsn> FOR [OUTPUT/INPUT] ....

OUTPUT in above stmt identifies that we are opening the file for writing.

INPUT in above stmt identified that we are opening the file for output.

CLOSE DATASET <dsn>.

Above stmt is used to close the file that is opened.

Apart from the above stmts, please keep note of stmts READ DATASET and TRANSFER.

READ DATASET - when we open a file for reading/uploading we use READ DATASET stmt.

Eg: READ DATASET <dsn> INTO <wa>.

TRANSFER - is the statement we use for writing data to a file.

Eg: TRANSFER <wa> TO <dsn>.

Source Code:

<b>Reading Data from Application Server</b>:

     open dataset fname for input in text mode encoding default.
     if sy-subrc ne 0.
        write:/ 'Unable to open file:', fname.
     else.
        do.
           read datasset fname into <wa>.
           if sy-subrc ne o.
              exit.
           else.
              append <wa> to itab.
           endif.
           close dataset fname.
        enddo.
     endif.

<b>Writing Data to Application Server</b>:

     open dataset fname for output in text mode encoding default.
     if sy-subrc ne 0.
        write:/ 'Unable to open file:', fname.
     else.
        loop at itab.
               transfer itab to fname.
        endloop.
        close dataset fname.
     endif.

Hope this info gives you some idea.

Kind Regards

Eswar

Re: what is open data set and close data set

anversha_s — Sat, 11 Nov 2006 09:31:30 GMT

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

Anver

if hlped pls mark points

Re: what is open data set and close data set

Former Member — Sat, 11 Nov 2006 09:43:06 GMT

Hello Chaitanya

The sequential files (ON APPLICATION SERVER) are called datasets. They are used for file handling in SAP.

OPEN DATASET [DATASET NAME] FOR [OUTPUT / INPUT / APPENDING]

IN [BINARY / TEXT] MODE

AT POSITION [POSITION]

MESSAGE [FIELD]

READ DATASET [DATASET NAME] INTO [FIELD]

DELETE DATASET [DATASET NAME]

CLOSE DATASET [DATASET NAME]

TRANSFER [FIELD] TO [DATASET NAME

Regards,

Raghav

Re: what is open data set and close data set

Former Member — Sat, 11 Nov 2006 09:46:43 GMT

Hi Chaitanya,

When ever we r trying to access the data from the application server we have to use open data set to read the data and close dataset for close that file.

AL11 is the tcode to see the file in sap Directory.

Murthy