topic Re: Data Dictionary?where does it reside? in Application Development and Automation Discussions

Data Dictionary?where does it reside?

Former Member — Thu, 19 May 2005 12:27:44 GMT

Hi all,

Where does the data dictionary reside in databse server or over database server?

Message was edited by: henry

Re: Data Dictionary?where does it reside?

Former Member — Thu, 19 May 2005 12:36:16 GMT

Hi Henry,

The data dictionary is an application. All the tables and the data is stored in the database server.

Regards,

Anand Mandalika.

Message was edited by: I029616

Re: Data Dictionary?where does it reside?

Former Member — Thu, 19 May 2005 13:22:30 GMT

Hi Henry,

The data dictionary comprises of many different tabels but here are some:

DD01L Domains

DD01T R/3 DD: domain texts

DD02L SAP tables

DD02T R/3 DD: SAP table texts

DD03L Table Fields

DD03T DD: Texts for fields (language dependent)

DD04L Data elements

DD04T R/3 DD: Data element texts

Regards,

Rob

Re: Data Dictionary?where does it reside?

Former Member — Thu, 19 May 2005 13:36:18 GMT

Mr.Anand,

I've posted these as diff threads.

if im inserting a record thru dialogue programming then the check table is checked..then it shud give short dump..just please expalin this(how does this work without short dump).

smartfroms/sapscripts or workbench dependent or independent..what does this mean.

Dispathcer makes the system understand, is there any other technical elabaration for this,if there is can you please do it.

thanks m regards

Re: Data Dictionary?where does it reside?

Former Member — Thu, 19 May 2005 13:46:52 GMT

Hi Henry,

What makes you think that there should be a short dump when the check tables are checked? Please explain wht your understanding is. That will help me explain better.

Regards,

Anand Mandalika.

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 04:40:54 GMT

Hi Anand,

that's my perception,want t0 clear that point,then it does nt give short dump?

all the check tables n the table in whihc Im inserting the record n at runtime the check tabel n the tabel in which im inserting are buffered,does nt this give short dump.

can u plz explain it.

all the check tables/foreign key tables/data reside in data dictionary?

thanks n regards

Message was edited by: henry

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 04:43:17 GMT

Hi Anand,

if te abov ething is nt happening then i think ...if im inserting record thru some program then check tabel is nt checked n the record in inseted directly,this does nt effect the rules of RDBMS itself.

thansk n regards

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 05:15:37 GMT

Hello Henry,

This is one of those questions that I used to have long time back when I was just beginning ABAP Programming. I'm know sure if this is the answer that you want to hear, but I will tell you what I have been able to gather -

You will not get a dump when you insert entries into a table which do not satisy the foreign key. The reason is that at the database server level, there's a setting (I don't know what that is, but it is dependent on the database that you are using) through which you can chose to ignore the foreign key check on the tables when the entries are inserted into the table. The primary key check (i.e., existence of duplicate entries) will have to be made for obvious reasons and cannot be disabled.

So when you insert entries that don't satisfy the foreign key relationship, the database server merely gives a kind of a warning, which the SAP Application Server ignores. If this were not the case, then the performance of the SAP system would have gone down considerably. Because, each time an record is inserted, all the checks have to be made. And these checks can sometimes be long chains which take up considerable amount of the CPU time on the Database Server.

If there were a hierarchy of say, 5 tables, and you choose to insert a record into the 5th one, it is indeed troublesome to check all the way up the hierarchy to see if the relevant entries are there in those tables.

There's also the concept of cascading delete. In the same hierarchy of 5 tables, if you delete an entry in the third table, then the entries in the 4th and the 5th tables which refer to this entry have to be deleted, since they are no longer valid. Obviously, this is going to turn into a major performance overhead and SAP doesn't use that.

As a result, most of the data-integrity issues are the responsibility of the programmer. We always hope that the Programmer understands the database concepts and uses good programming practices.

I know you're going to say that data integrity is being compromised, but I must tell you that it is a trade-off between performance and data integrity.

This is where dialog programming comes to the rescue of the users. If a user unknowingly enter an incorrect value on a field, which would subsequently be entered into a database table, then SAP does provide assistance by (at the application layer) doing some basic checks to help the user. But if the ABAP programmer himself tries to enter data directly (which is strongly discouraged), then there's simply nothing that can be done. The programmer is choosing to violate the data integrity.

Hmmmmm... this has been so long a post that I could have written a weblog on this. But I can still do that! And I will try to do some research and add in a few more details in that. I will remmeber to send you the link then.

Regards,

Anand Mandalika.

P.S. I have liked this question. A perfect one for beginners (and even the experienced guys??? )

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 11:16:43 GMT

Hi Anand,

It's fr the experienced guys too.It's a marvalous explanation I've ever got.

I'll close this is thread as solved the issue by u,bt one last clarification,'good programming' does this mean taking the data-integrity issue into consideration while programming or?

whatever u said I agree on.great patience,Iadvice u to have a weblog,SAP AG to appreciates it.

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 17:36:36 GMT

I disagree to certain extent with Anand's explaination that it is due to some setting at DB server level setting that SAP manages to ignore Foreign Keys while making updates .

The way I know it, SAP never actually creates any Foreign Key constraint at the DB level at all.

SAP only use it as indicators to implement the foreign key logic in it's own dialogue programs.

But if not written explicitly Reports can violate the indicator.

In case SAP would create it ( it never does )as a constraint at DB level, then as per Henry's apprehension, there might would have been run time errors, if a foreign key is violated.

Similar explanation is true for why SAP does not support cascading deletes.

Good Question Henry.

Thanks,

Ram

Re: Data Dictionary?where does it reside?

Former Member — Fri, 20 May 2005 17:48:24 GMT

Ram,

You are correct in saying that SAP does not create any foreign constraints at the native database level. All that is in SAP data dictionary and is handled by SAP application layer.

Now, coming to Henry's issue, if you directly do an insert into the database table without going through the application logic, the record will get inserted into the table without any error. But when you try to access it in any form other than a program, you have to go through the application layer, it is bound to give you an error. Because, at this time, the application layer validates the data that it is bringing on to the screen and it sees that your previous insert has violated the foreign key restrictions.

That is one of the reasons why you don't directly insert into SAP standard tables. If you do it, you have to perform all the validations, including foreign key constraints(if any) by yourself, before inserting the data.

Srinivas

Re: Data Dictionary?where does it reside?

Former Member — Sat, 21 May 2005 14:06:31 GMT

Hi Anand/Ram/Adavi/all

thanks a lot for ur valuable knowledge sharing.

can u please elaborate abotu the 'indicator' which u were talking off.

thanks n regards

Message was edited by: henry

Re: Data Dictionary?where does it reside?

Former Member — Sat, 21 May 2005 18:03:22 GMT

Hi Henry,

Here indicator means guideline only , not exactly a technical term.

When you create/change table definition through SE11 at that time you can indicate that this field should be checked with entries of some other table ( Called as check table ).

e.g Open the table T005G ( Contains Client, Country & City ) in Xn SE11 and select the country field --> press key symbol ( to see the check table defined for field Country).

In the next screen you will see that table T005 ( Country Master table ) is defined as a check table for this field.

This means that any country code that you want to insert / update into T005G should already be existing in T005.

If you are writing a dialogue program to get data from the screen and then insert into T005G then SAP will take care of this check.

But if you are writing a report ( or whatever ) and forcing data save into T005G using Insert or Update SQL statements, then SAP will not be able to stop you from doing that. So it's your responsibilty to implement these checks in your application programs explicitly.

Thanks,

Ram

Re: Data Dictionary?where does it reside?

Former Member — Tue, 24 May 2005 06:15:42 GMT

Hi Ram,

thanks a lot,and appreciate ur answer/explanation.

If u think there is anyhting else to know in this aspect, then Ill keep it open or else i'll make it solved the problem.

thanks n regards

Re: Data Dictionary?where does it reside?

Former Member — Tue, 24 May 2005 09:05:17 GMT

A Data Dictionary is a central source of information for the data in a data management system. Its main function is to support the creation and management of data definitions.

It resides in the Application Server.

Re: Data Dictionary?where does it reside?

Former Member — Tue, 24 May 2005 09:12:23 GMT

Hi Ram,

MR .Dinesh B.()please look into it )please look at the following/above,that data dictionay resides in app server.

I think se11(data dictionay ) is an application in sap n allthe data resides in database,is nt it so?

thanks n regards

Re: Data Dictionary?where does it reside?

Former Member — Tue, 24 May 2005 16:40:44 GMT

Hi Henry,

There are lot many other things that you will come to know / ask when you will actually go into deep.

Like the types of foreign keys...complete, generic key blah blah..

Cardinality...I am not sure if I got the term correctly.

Value Table & Check table differences ...

you know what, you can do your job without even knowing it. But it's good to know.

I'll suggest you try to create or display a table in SE11 & look for a check table and see all these features by pressing F1 on the fields.

And in case you need any help ..I don't have to tell you.

I can see that you are a master in asking questions.

I must say I'm impressed with your ability to raise questions...And I think after 4-5 days you will be writing a book called How to learn ABAP/5 in 10 days

I am just in a good mood today and I posted 3-4 answers with a smiley at the end. All useless

Cheers,

Ram

Re: Data Dictionary?where does it reside?

Former Member — Tue, 24 May 2005 16:57:28 GMT

Sorry I missed your last question.

Actually Data Dictionary is the term for the Application Program( Set of programs , GUI interfcaes etc etc ..) that you use to create / change / display database tables / structures / data elements / domains etc..

So data dictionary in itself resides on Application Server ..like all other ABAP programs.

It's program and it does simple things . Like if you want to create a table , then in SE11 you just need to fill up fields ,data elements ....like you are filling up an excel sheet. Specify tablespaces , size category etc...and then DDIC ( a program ) will just create a database statement for whatever you did.

Something like you must have done while working directly with databases ...Further that will be executed at db level to actually create a database table in db.

CREATE TABLE Z..{FIELD .. }..TABLESPACE.. MAXEXTENT ..

But whatever DDIC creates / Change / Display , is basically some data, index or a database table in itself and so on...And that will obviously be getting created in the Database.

Well , there might be exceptions like Views and a few others, which might not get created at database level always.

Thanks,

Ram

Re: Data Dictionary?where does it reside?

Former Member — Wed, 25 May 2005 05:54:38 GMT

Hi Ram,

can u plz take me thru by what xactly it is if u say'tha t data dictionay resides in application server and the table/data resides in data base and views again in application server'

does all these reside in application server as runtime object or ?

the program names and codes are stored in some tables..all these are also reside in app server..?

is there any rule or anything like that ,that such things(objects) shud reside in app server n such things(objects) in db sever

please take me thru this.

thanks n regards

Re: Data Dictionary?where does it reside?

Former Member — Wed, 25 May 2005 06:01:58 GMT

data dictionay resides in app server then what about the tables/data?where do these objects reside?

thanks n regards