topic Re: general in Application Development and Automation Discussions

general

Former Member — Mon, 04 Jun 2007 09:28:57 GMT

what r logical databases

Re: general

Former Member — Mon, 04 Jun 2007 09:33:55 GMT

Hi,

Logical databases are special ABAP programs that retrieve data and make it available to application programs. The most common use of logical databases is still to read data from database tables by linking them to executable ABAP programs.

For More Info,

http://help.sap.com/saphelp_nw04s/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm

Regards,

Padmam.

Re: general

Former Member — Mon, 04 Jun 2007 09:35:42 GMT

Hi,

A logical database is a special ABAP/4 program which combines the contents of certain database tables. You can link a logical database to an ABAP/4 report program as an attribute. The logical database then supplies the report program with a set of hierarchically structured table lines which can be taken from different database tables.

GET will fetch the table data immediately

GET LATE

In the LDB when you define the table structure in hierarchy, first it will fetch the higher node data and then all the below node tables data and comes to a second record in the top node table. for this GET Late is used.

You can create any number of primary keys in a table

GO THROUGH LINKS -

http://www.sap-basis-abap.com/saptab.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/c6/8a15381b80436ce10000009b38f8cf/frameset.htm

/people/srivijaya.gutala/blog/2007/03/05/why-not-logical-databases

www.sapbrain.com/FAQs/TECHNICAL/SAP_ABAP_Logical_Database_FAQ.html

www.sap-img.com/abap/abap-interview-question.htm

www.sap-img.com/abap/quick-note-on-design-of-secondary-database-indexes-and-logical-databases.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm

http://help.sap.com/saphelp_nw2004s/helpdata/en/9f/db9bb935c111d1829f0000e829fbfe/content.htm

Regards,

Priyanka.

Re: general

Former Member — Mon, 04 Jun 2007 09:35:55 GMT

Hi Manjula,

Logical databases are SAP standard programs that are desinged with selections screens that helps easy retrival and access of data from various tables in and efficient manner.

You can get to know more about the logical databases from the SAP documentation or the following links.

Advantages of Logical database -

1) No need of programming for retrieval , meaning for data selection

2) Easy to use standard user interface, have check completeness of user input.

Disadvantages

1) Fast in case of lesser no. of tables But if the table is in the lowest level of hierarchy, all upper level tables should be read so performance is slower.

GO THROUGH LINKS -

http://www.sap-basis-abap.com/saptab.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/c6/8a15381b80436ce10000009b38f8cf/frameset.htm

Award points if helpfull

Regards,

Omkar.

Re: general

Former Member — Mon, 04 Jun 2007 09:37:33 GMT

hi,

logical databases are used for grouping two or more databses into a single unit and we can easily access data from them using put n get parameters.

get parameter is used in the calling prgm and it internally triggers put parameter in logical database.

if helpful reward some points.

with regards,

suresh.

Re: general

Former Member — Mon, 04 Jun 2007 09:40:36 GMT

Hi,

Logical database are programs that predefine a structured access to table and structure. There are mainly used in HR.

You create/maintain those via SE36 or SLDB.

You use them in program linking then in program attributes and using GET instructions or by using FM LDB_PROCESS.

For definition of logical database look at

http://help.sap.com/saphelp_46c/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm

For creation/editing look at http://help.sap.com/saphelp_46c/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm

For using these in Abap http://help.sap.com/saphelp_46c/helpdata/en/60/183d78163011d2953c0000e8353423/frameset.htm

Re: general

Former Member — Mon, 04 Jun 2007 09:57:26 GMT

http://help.sap.com/saphelp_46c/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm

it shows the diagramatic view

Re: general

sreeramkumar_madisetty — Mon, 04 Jun 2007 10:00:51 GMT

Logical Databases

However, from Release 4.5A, it has also been possible to call logical databases using the function module LDB_PROCESS. This allows you to call several logical databases from any ABAP program, nested in any way. It is also possible to call a logical database more than once in a program, if it has been programmed to allow this. This is particularly useful for programs with type 1.

Logical databases contain Open SQL statements that read data from the database. You do not therefore need to use SQL in your own programs. The logical database reads the program, stores them in the program if necessary, and then passes them line by line to the application program or the function module LDB_PROCESS using an interface work area.

Logical Databases - Views of Data

A logical database provides a particular view of database tables in the R/3 System. It is always worth using logical databases if the structure of the data that you want to read corresponds to a view available through a logical database.

The data structure in a logical database is hierarchical. Many tables in the R/3 System are linked to each other using foreign key relationships. Some of these dependencies form tree-like hierarchical structures. Logical databases read data from database tables that are part of these structures.

Regards,

Sree

Re: general

Former Member — Mon, 04 Jun 2007 10:03:52 GMT

Hi,

The LDB is special type of ABAP program that combines the contents of certain related database tables and retrieve some related data and make it available to application programs.

PNP is LDB used in HR and SAPDBPNP is the database program for the logical data base PNP.

Thanks

Srinu

Re: general

Former Member — Mon, 04 Jun 2007 10:06:15 GMT

LDB = Selection screen +

Database tables +

Logic to extact data based on selection screen input.

Generally LDB's are used in SAP-HR. It will be always associated with get and set events.

All the very best to you.

Regards,

-Mohan.

Re: general

Former Member — Mon, 04 Jun 2007 10:09:11 GMT

Hi Manjula,

Check this URL..

About Logical Database.

http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm

Logical database-design, normalisation rules

http://www.sum-it.nl/cursus/dbdesign/english/logis010.php3

Hope it helps you.

Reward for all useful answers.

Regards,

Jackie..

Re: general

Former Member — Mon, 04 Jun 2007 10:16:58 GMT

Hi,

Logical Databases

Logical databases are special ABAP programs that read data from database tables. They are

used by executable (type 1) programs. At runtime, you can regard the logical database and the

executable program (reports) as a single ABAP program, whose processing blocks are called by

the runtime environment in a particular, pre-defined sequence.

You edit logical databases using a tool within the ABAP Workbench, and link them to executable

programs (reports) when you enter the program attributes. You can use a logical database with

any number of executable programs (reports). From Release 4.5A, it is also possible to call

logical databases on their own.

Structure of a Logical Database

The following diagram shows the structure of a logical database, which can be divided into three

sections:

Structure

The structure of a logical database determines the database tables which it can access. It adopts

the hierarchy of the database tables defined by their foreign key relationships. This also controls

the sequence in which the tables are accessed.

Selection Part

The selection part of the logical database defines input fields for selecting data. The runtime

environment displays these on the selection screen when you run an executable program linked

to the logical database. The corresponding fields are also available in the ABAP program,

allowing you, for example, to change their values to insert default values on the selection screen.

Database Program

The database program of a logical database is a container for special subroutines, in which the

data is read from the database tables. These subrotuines are called by the reporting processor in

the runtime environment in a predefined sequence.

Running Type 1 Programs with a Logical Database

The runtime environment calls depend both on the structure of the logical database and on the

definition of the executable program. The structure of the logical database determines the

sequence in which the processing blocks of the logical database are called. These in turn call

GET event blocks in the executable program. These GET event blocks determine the read depth

in the structure of the logical database. TABLES or NODES statements in the declaration part of

the executable program determine which of the input fields defined in the logical database are

included in the selection screen. They also define interface work areas for passing data between

the logical database and the executable program.

The actual access to the R/3 System database is made using OPEN SQL statements in the

PUT_<TABLE> subroutines. The data that is read is passed to the executable program using the

interface work areas (defined using the TABLES statement). Once the data has been read in the

logical database program, the executable program (report) can process the data in the GET

event blocks. This technique separates data reading and data processing.

Uses of Logical Databases

The main use of logical databases is to make the code that accesses data in database tables

reusable. SAP supplies logical databases for all applications. These have been configured for

optimal performance, and contain further functions such as authorization checks and search

helps. It is appropriate to use logical databases whenever the database tables you want to read

correspond largely to the structure of the logical database and where the flow of the system

program (select - read - process - display) meets the requirements of the application.

Regards,

Bhaskar