questions on data dictionary

DATA DICTIONARY

1. What are the layers of data descriptions in R/3?
• The external layer
• The ABAP/4 layer
• The database layer

2. Define external layer.
The external layer is the plane at which the user sees and interacts
With the data, that is, the data format in the user interface. This data
Format is independent of the database system used.

3. Define ABAP/4 layer?
The ABAP/4 layer describes the data formats used by the ABAP/4 processor.

4. Define Database layer ?
The database layer describes the data formats used in the database.

5. What is a Data Class?
The Data class determines in which table space the table is stored when it is created in the database.

6. What is a Size Category?
The Size category describes the probable space requirement of the table in the database.

7. How Many types of size categories and data classes are there?
There are five size categories (0-4) and 11 data classes, only three of which are appropriate for application tables:
- APPL0 - Master data (data frequently accessed but rarely updated)
- APPL1 - Transaction data (data that is changed frequently)
- APPL2 - Organizational data (customizing data that is entered when system is Configured and then rarely changed)
The other two types are:
- USR
- USR1 - Intended for customers own developments

8. What are control tables?
The values specified for the size category and data class are mapped to database-specific values via control tables.

9. What is the function of the transport system and workbench organizer?
The function of the transport system and the Workbench Organizer is to manage any changes made to objects of the ABAP/4 Development Workbench and to transport these changes between different SAP systems.

10. What is a table pool?
A table pool (or pool) is used to combine several logical tables in the ABAP/4 Dictionary. The definition of a pool consists of at least two keys Fields and a long argument field (VARDATA).

11. What are pooled tables?
These are logical tables which must be assigned to a table pool when they are defined. Pooled tables can be used to store control data (such as Screen sequences or program parameters).

12. What is a table cluster?
A table cluster combines several logical tables in the ABAP/4 Dictionary. Several logical rows from different cluster tables are brought together in a single physical record. The records from the cluster tables assigned to a cluster are thus stored in a single common table in the database.

13. How can we access the correction and transport system?
Each time you create a new object or change an existing object in the ABAP/4 Dictionary, you branch automatically to the Workbench Organizer or correction and transport system.

14. Which objects are independent transport objects?
Domains, Data elements, Tables, Technical settings for tables, Secondary indexes for transparent tables, Structures, Views, Match code objects, Match code IDs,Lock objects.

15. How is conversion of data types done between ABAP/4 & DB layer?
Conversion between ABAP/4 data types and the database layer is done within the database interface.

16. How is conversion of data types done between ABAP/4 & external level?
Conversion between the external layer and the ABAP/4 layer is done in the SAP dialog manager DYNP.

17. What are the Data types of the external layer?
ACCP, CHAR, CLNT, CUKY, CURR, DATS, DEC, FLTP, INT1, INT2, INT4, LANG, LCHR, LRAW, NUMC, PREC, QUAN, RAW, TIMS, UNIT, VARC.

18. What are the Data types of the ABAP/4 layer?
Possible ABAP/4 data types:
C: Character.
D: Date, format YYYYMMDD.
F: Floating-point number in DOUBLE PRECISION (8 bytes).
I: Integer.
N: Numerical character string of arbitrary length.
P: Amount or counter field (packed; implementation depends on hardware
platform).
S: Time stamp YYYYMMDDHHMMSS.
T: Time of day HHMMSS.
V: Character string of variable length, length is given in the first
two bytes.
X: Hexadecimal (binary) storage.

18. How can we set the tablespaces and extent sizes ?
You can specify the extent sizes and the tablespace (physical storage area in the database) in which a transparent table is to be stored by setting the size category and data class.

19. What is the function of the correction system?
The correction system manages changes to internal system components, such as objects of the ABAP/4 Dictionary.

20. What are local objects?
Local objects (Dev class $TMP) are independent of correction and transport system.

21. What is a Development class?
Related objects from the ABAP/4 repository are assigned to the same development class.This enables you to correct and transport related objects as a unit.

22. What is a data dictionary ?
Data dictionary is a central source of data in a data management system. Its main function is to support the creation and management of data definitions. It has details about
- What data is contained ?
- What are the attributes of the data ?
- What is the relationship existing between the various data elements ?
23. What functions does a data dictionary perform ?
In a data management system, the principal functions performed by the data dictionary are
- Management of data definitions
- Provision of information for evaluation
- Support for software development
- Support form documentation
- Ensuring that the data definitions are flexible and up-to-date.

24. What are the features of ABAP/4 Dictionary ?
The most important features are :
- Integrated to ABAP/4 Development Workbench
- Active in the runtime environment

25. What are the uses of the information in the Data dictionary ?
The following information is directly taken from the Data dictionary :
- Information on fields displayed with F1 help
- Possible entries for fields displayed with F4 help
- Matchcode and help views search utitlities.

26.What are the basic objects of the data dictionary ?
- Tables
- Domains
- Data elements
- Structures
- Foreign keys
27. What are the aggregate objects in the data dictionary?
- Views
- Match codes
- Lock objects

28.In the ABAP/4 Dictionary Tables can be defined independent of the underlying database (T/F)
True

29. ABAP/4 Dictionary contains the Logical _ (Logical/Physical) definition of the table.

30. A field containing currency amounts (data type CURR) must be assigned to a reference table and a reference field. Explain.
As a reference table, a system table containing all the valid currencies is assigned or any other table which contains a field with the currency key format. This field is called as reference field.
The assignment of the field containing currency amounts to the reference field is made at runtime. The value in the reference field determines the currency of the amount.

31. A field containing quantity amounts (data type QUAN) must be assigned to a reference table and a reference field. Explain.
As a reference table, a system table containing all the valid quantity units is assigned or any other table which contains a field with the format for quantity units (data type UNIT). This field is called as reference field.
The assignment of the field containing quantity amounts to the reference field is made at runtime. The value in the reference field determines the quantity unit of the amount.

32. What is the significance of Technical settings (specified while creating a table in the data dictionary) ?
By specifying technical settings we can control how database tables are created in the database.
The technical settings allows us to
- optimize storage space requiremnets
- table access behaviour
- buffering required
- changes to entries logged

33.What is a Table attribute ?
The table attributes determine who is responsible for maintaining a table and which types of access are allowed for the table. The most important table attributes are:
a. Delivery class
b. Table maintenance allowed
c. Activation type.

34. What is the significance of Delivery Class ?
- The delivery class controls the degree to which the SAP or the customer is responsible for table maintenance
- whether SAP provides the table with or without contents.
- determines the table type.
- determines how the table behaves when it is first installed, at upgrade, when it is transported, and when a client copy is performed.

35. What is the maximum number of structures that can be included in a table or structure
- Nine.

36. What are the two methods of modifying Sap standard tables ?
- Append Structures and
- Customizing Includes.

39. What is the difference between a Substructure and an Append Structure ?
- In case of a substructure, the reference originates in the table itself, in the forma of a statement .include... .
- In case of an append structure, the table itself remains unchanged and the refrence originates in the append structure.

40. To how many tables can an append structure be assigned ?
- One.

41. If a table that is to be extended contains a long field, we cannot use append structures. Why?
Long fields in a table must always be located in the end, as the last field of the table. If a table has an append structure the append line must also be on the last field of the table.

42.Can we include customizing include or an append structure with Pooled or Cluster tables ?
- No.

43. What are the two ways for restricting the value range for a domain ?
- By specifying fixed values.
- By stipulating a value table.

44. Structures can contain data only during the run time of a program (T/F)
- True.

45. What are the aggregate objects in the Dictionary?
- Views
- Match Code
- Lock object

46.What are base tables of an aggregate object?
The tables making up an aggregate object (primary and secondary) are called aggregate object.

47.The data of a view is not physically stored, but derived from one or more tables. (T/F).
-True.

48. What are the 2 other types of Views, which are not allowed in Release 3.0?
- Structure Views
- Entity Views.

49. What is a Match Code?
Match Code is a tool to help us to search for data records in the system. Match codes are an efficient and user-friendly search aid where key of a record is unknown.

50. What are the two levels in defining a Match Code?
- Match Code object
- Match Code Id.

51. What is the maximum number of match code Id's that can be defined for one Match code object ?
- 36. A match code Id is a one character ID that can be a letter or a number.

52. . Can we define our own Match Code ID's for SAP Matchcodes ?
Yes, the numbers 0 to 9 are reserved for us to create our own Match Code IDs for a SAP defined Matchcode object.

53. What is an Update type with reference to a Match code ID?
If the data in one of the base tables of a matchcode ID changes, the matchcode data has to be updated. The update type stipulates when the matchcode is to be updated and how it is to be done. The update type also specifies which method is to be used for Building matchcodes . You must specify the update type when you define a matchcode ID.

54. Can matchcode object contain IDs with different update types ?
- Yes.

55. What are the update types possible ?
The following update types are possible:
• Update type A: The matchcode data is updated asynchronously to database changes.
- Update type S: The matchcode data is updated synchronously to database changes.
- Update type P: The matchcode data is updated by the application program.
- Update type I: Access to the matchcode data is managed using a database view.
- Update type K: Access to the matchcode is achieved by calling a function
module.

56. What are the two different ways of building a match code object ?
A match code can be built in two different ways :
- Logical structure : The matchcode data is set up temporarily at the moment when the match code is accessed. (Update type I, K)
- Physical structure : The match code data is physically stored in a seperate table in the database. (Update type A, S, P)

57. What are the differences between a Database index and a match code ?
- Match Code can contain fields from severeal tables whereas an index can contain fields from only one table.
- Match code objects can be built on transparent tables and pooled and cluster tables.

58. What is the function of a Domain?
- A domian describes the technical settings of a table field.
- A domain defines a value range, which sets the permissible data values for the fields, which refers to this domain.
- A single domain can be used as basis for any number of fields that are identical in structure.

59. Can you delete a domain which is being used by data elements ?
- No.

60. What are conversion routines ?
- Non standard conversions from display format to sap internal format and vice-versa are implemented with so called conversion routines.

61. What is the function of a data element ?
- A data element describes the role played by a domain in a technical context. A data element contains semantic information.

62. Can a domain, assigned to a data element be changed ?
- Yes. We can do so by just overwriting the entry in the field domain).

63. Can you delete data element which is being used by table fields .
- No.

64. Can you define a field without a data element ?
- Yes. If you want to specify no data element and therefore no domain for a field, you can enter data type and field length and a ashort text directly in the table maintenance.

65. What are null values ?
- If the value of a field in a table is undefined or unknown, it is called a null value.

66. What is the difference between a structure and a table ?
- Structures are constructed the almost the same way as tables, the only difference using that no database table is generated from them.

67. What is a View ?
- A view is a logical view on one or more tables. A view on one or more tables i.e, the data from a view is not actually physically stored instead being derived from one or more tables.

68. How many types of Views are there ?
- Database View
- Help View
- Projection View
- Maintenance View

69. What is Locking ?
- When two users simultaneously attempt to access the same data record, this is synchronised by a lock mechanism.


70. What is database utility ?
- Database utility is the interface betweenn the ABAP/4 Dictionary and the underlying the SAP system.

71. What are the basic fucntions of Database utility ?
The basic functions of database utility are :
- Create database objects
- Delete database objects
- Adjust database objects to changed ABAP/4 dictionary definition.

72. What is Repository Info. Systems ?
It is a tool with which you can make data stored in the ABAP/4 Dictionary available.


and some more questions :


1. What represents the commercially oriented model of the real world? (A.02.3)
SAP’s Enterprise Data Model (EDM) represents the commercially oriented model of the real world, while the ABAP Dictionary contains the data processing-oriented model. The EDM is the top-level overview of the entire system. At this level the exact characteristics of the relationships between entities are not important, merely knowing that the relationships exist is what matters.

2. What is an entity? How are entities represented in the ABAP Dictionary? (A.02.6, A.02.9)
An entity is an object that is of interest and is uniquely identifiable. It is an object about which information must be stored. Within the ABAP Dictionary, entities are stored as records in a table.

3. What is an entity type? How are entity types represented in the ABAP Dictionary? (A.02.8, A.02.9)
Entity types describe a set of entities with common attributes. Each entity type has a unique name and unique description. For example, the set of all customers would be an entity type, while each individual customer would be an entity in that type. Within the ABAP Dictionary, entity types are stored as tables.

4. What is an attribute? How are attributes represented in the ABAP Dictionary? (A.02.7, A.02.9)
Attributes describe an entity’s (or entity type’s) features or characteristics. Within the ABAP Dictionary, attributes are represented as fields in a table.

5. How are business rules represented in a data model? (A.02.10)
Business rules are represented in a data model by relationships between entity types. The cardinality and category of those relationships help define those rules. Within the ABAP Dictionary, these relationships are implemented as foreign key relationships.

6. Name and describe the 5 entity relationship categories. (A.02.26-A.02.31)
A. Hierarchical: an entity type is dependent on the existence of exactly one other entity
type. In this case the primary key of the referenced entity type is inherited by the
dependent entity type.
B. Aggregating/Associative: an entity type is dependent on the existence of multiple other entity types. This type is used to resolve many-to-many relationships. The full primary keys of the referenced entity types are inherited by the dependent entity type.
C. Referential: an entity type refers to another entity type but is not identified by the
relationship. It is possible to change or eliminate the relationship, but as long as the relationship exists, it is non-optional. The primary key of the referenced entity type is passed onto the dependent entity type as a non-key field.
D. Conditional-Referential: the same as a referential relationship, but the relationship is optional.
E. Specialization: an entity type which represents a subset of the referenced entity type but also has additional attributes. In this case the referenced entity type is called the generalization, and the dependent entity type is called the specialization. Generalizations and specializations have the same primary key fields but are used to store different information in non-key fields.

7. How is the SAP Enterprise Data Model linked to the ABAP Dictionary? (A.02.33)
Via the SAP Data Modeler.

8. What within R/3 manages data definitions? (1.01.3-1.01.7)
The ABAP Dictionary manages data definitions so that all data is described centrally and without redundancy, thereby maintaining data integrity (all changes take immediate effect in all relevant modules and need only be entered in one location).

9. What is the DB Utility? What is its transaction code? (1.01.9)
The database utility is the interface between the data dictionary and the relational database that underlies the SAP system. It is used to create underlying tables in the database which will be used in SAP. The DB utility supports tables, table indexes, views, matchcodes, pools/clusters. Certain overview functions are provided: background logs, background jobs, restart logs. The processing options offered are online, background and generate program (where the program that is to execute the selected function is generated without actually executing the function). The basic functions of the DB utility are create, delete and convert, and delete, create again. There is a lock mechanism associated with the DB utility in order to ensure that an existing operation may be completed before another is triggered.
The transaction code for the DB utility is SE14.

10. Explain the concept of tables, domains and data elements. (1.02.4-1.02.17)
A domain is used to group together fields of similar technical characteristics. Attributes such as format (data type), length, and output characteristics are specified by the domain. A data element must be associated with a domain, and it gives a meaningful description to a field in a particular context. Tables consist of records (rows) and fields (columns). Each field in a table must be assigned to a data element (which is in turn assigned to a domain).

11. At the domain level, what within R/3 prevents the user from entering invalid data? (1.02.16, 1.02.19)
1. Value table, 2. Explicit values

12. Within the ABAP Dictionary, what ensures data integrity between tables?
Foreign key relationships.

13. Which attributes of the answer to #12 help further define relationships between tables?
Name and describe the two components of those attributes. (1.03.10-1.03.14)
The semantic attributes of foreign key relationships help further define business rules and enforce data integrity. Those two attributes are cardinality (how many of one item relate to how many of another) and foreign key field type (similar to relationship categories in the Data Modeler).

14. What is the purpose of the ABAP Repository Information System? (1.06.3)
The ABAP Repository Information System allows the retrieval of information about development objects.


15. What are the basic types of queries made to the Repository Information System? (1.06.3)
-- Find
-- Where-Used
-- Modification analyses (i.e. all objects X modified by user Y)

16. What four basic types of objects can you search for using the R/3 Repository Information System? (1.06.11)
Modeling objects, programming objects, ABAP Dictionary objects, and environment objects.

17. What is a foreign key and how is it used? (1.03.3,1.03.4)
A foreign key is a field that provides a link between two tables by including a reference in the first table (dependent or foreign key table) to the primary key of the second table (check table). The dependent (foreign key) table may use only those values contained in the check table. The foreign key relationship is set up in the ABAP Dictionary at the field level. The foreign key field and the check table field must have the same domain. An important function of foreign keys is to support data integrity.

18. What is a search help? What are the two stages of creating a collective search help? (1.09.3, 1.09.10)
A search help is a tool to help find data records stored in the SAP system. It is used as online help (F4) or as a search aid when an entry field calls for a key and only certain other (non-key) fields of the object are known. (i.e. You want to research an employee and know his name but can’t remember his personnel number, so a matchcode search on his name can help you find the number).
First the elementary search helps are defined with the relevant table and fields specified. The collective search help is then defined using multiple elementary search helps.

19. Tables defined in the ABAP Dictionary can be assigned to what 5 specific data classes (via the technical settings screen)? (1.04.9)
Master data, transaction data, organization and customizing data, system data, and user (customer) data.

20. Name and describe the five table types. Which one is sometimes not considered
a true table type? (1.04.3-1.04.7)
STRUCTURE (INTTAB): internal structure without mapping to an underlying database table. Field strings used by ABAP as structures. Can be used in multiple tables.
TRANSP: An SAP data dictionary table which is mapped 1:1 to the database. Designed to hold SAP data in a database.
POOL: logical pooled table used to store internal control data not relevant externally. Mapped as many database tables to one SAP table.
CLUSTER: logical cluster table used to store continuous texts (documentation data).
VIEW: a method of viewing database tables. Can combine data from multiple tables into one view, and/or can restrict the view to certain records or fields within a table. Views are sometimes not considered true table types.

21. What are the four technical settings of a transparent table? (1.04.8-1.04.13)
Data class: physical area in the database to which the table is assigned.
Size Category: space required for the table in the db (defines the size of the disk space
allocated for the table)
Buffering: whether and how to be buffered (suggested for tables not changed very
often); tables can have full or partial buffering
Log data changes: (on or off) keeps track of the modifications to a table. If logging is on
a copy of data is saved from before changes as well as after.

22. After a table is created, can its technical settings be changed? If so, when? (1.04.13)
Yes. It is now possible to change the technical settings of an active table and reactivate the table at any time. This is a change from version 2.2 to version 3.0 of SAP.

23. What utility supports the creation of tables and secondary indexes? (1.04.14)
The database utility. This utility is invoked automatically upon table activation or can be invoked directly from the ABAP Dictionary maintenance screens.

24. What are the possible cardinalities of a foreign key? (1.03.10, A.01.3-A.01.7)
The relationship is n:m where n refers to the relationship from the foreign key table to the check table and can have values 1 or C (none or 1), and m refers to the relationship from the check table to the foreign key table and can have values 1, C (none or 1), N (1 or many) or CN (none, 1 or many).
The possible cardinalities are 1:1, 1:C, 1:N, 1:CN, C:1, C:C, C:N, and C:CN. The most commonly used cardinalities are 1:1, 1:C, 1:CN, and C:CN.

25. Names of data dictionary objects are limited to how many characters? (1.02.4)
Restricted to 30. 30 characters are allowed for tables. Search Helps -- 30, logical databases--20, program names -- 40, type groups -- 5.

26. What is the purpose of a type group? (1.11.3, 1.11.4)
Type groups allow the user to define their own data types within the ABAP dictionary. These data types are then available for use in any ABAP program.