Defining Basic Attributes of Fields

The functions Add Field and Modify Field can also be called from within the function Edit elements of a File with the editor line command .E. See the section Editors in Predict in the Predict Reference documentation.

This document covers the following topics:

• Add/Copy/Modify Screen

• Field Type

• Level Number

• Field Format

• Character Set

• Character Set - Adabas

• Field Length

• Descriptor Type

• Descriptor Type - continued

• Maximum Number of Values / Occurrences

• Unique Option

• Field Short Name

• Suppression / Null Value Option

• Variable Length Option - IMS

• Null Default Option

• Natural Field Length

• Do Not Convert Option

• Related Standard File

• Check against standard

• Natural Attributes

• Hidden

• Additional attributes / Associations

Most attributes are applicable to fields of all file types.

Basic attributes applying to different field types are described below. Type-specific attributes are described in the section Defining Derived Fields.

Add/Copy/Modify Screen

The following screen is displayed for the functions Add/Copy/Modify Field.

13:29:09             *****  P R E D I C T  *****                     2009-07-31
                              - Add a Field -                                  
Field ID ........ HNO-EL-A                                                     
File ID ......... HNO-FI-A                                                     
Keys ..                                                                 Zoom: N
                                                                               
Ty L Field ID                         F Cs Length   Occ   D U DB S NAT-l Cnv   
*- - -------------------------------- *- * -------- ----- * * -- * ----- ---   
   1 HNO-EL-A                                                 AA N             
                                                                               
                                                                               
                                                                               
                                                                               
Natural attributes                                                             
  Header1 ..................                                                   
  Header2 ..................                                                   
  Header3 ..................                                                   
  Index on PE group level ..           Dynamic length .....                    
  Edit mask ........                                                           
Abstract     Zoom: N                                                           
                                                                               
                                                                               
  Additional attributes ..* N          Associations ..* N                      

The screen for maintaining fields of SQL file types contains some different attributes and is shown below.

Possible Types of Fields

The table below lists all possible types of the object type field.

Add/Copy/Modify Screen for SQL Fields

The following screen is displayed for the functions Add/Copy/Modify Field and applies to SQL file types.

 17:11:27             *****  P R E D I C T  *****                     2009-07-31
                               - Add a Field -                                  
 Field ID ........ HNO_EL_S                                                     
 File ID ......... HNO-DB2                                                      
 Keys ..                                                                 Zoom: N
                                                                                
 Ty L Field ID                         F Cs Length   Occ   D U N Df NAT-l       
 *- - -------------------------------- *- * -------- ----- * * * *- -----       
    1 HNO_EL_S                                                 U                
                                                                                
                                                                                
                                                                                
                                                                                
 Natural attributes                                                             
   Header1 ....                                                                 
   Header2 ....                                                                 
   Header3 ....                                                                 
   Edit mask ..                                                                 
 Hidden .......   (Y/N)                                                         
 Abstract     Zoom: N                                                           
                                                                                
                                                                                
   Additional attributes ..* N          Associations ..* N                      

Field Type

The field type is indicated in the column Ty of the Add/Copy/Modify screen. The following types can be specified:

If HM, HP, HQ, HY, OD, PH, SB or SP is specified, an additional input screen is displayed. See Defining Derived Fields.

See also section ADACMP (COMPRESS-DECOMPRESS) in the Adabas Utilities documentation.

Redefining Fields

See Redefine Field - Code R.

Defining Periodic Groups in Periodic Groups

• Within a redefinition, nested periodic groups (PE within a PE) can be defined in files of all types.

• Outside of a redefinition, nested periodic groups can only be defined in files of the following types:

  S	Sequential file
  C	Conceptual file
  M	ISAM file
  Z	Standard file
  O	Other file

Level Number

The level number of the field is indicated in the column L of the Add/Copy/Modify screen. The level number is used to define a group structure. Level numbers 1 to 9 can be used (except for Adabas files, see below).

• The level number must be increment by 1 immediately following a field of type RE, PE, PC or GR.

• For redefinitions, the level number must be at least one greater than the level number of the field being redefined. See Redefine Field - Code R.

Adabas Files

The following rules apply to level numbers for Adabas files:

• The PE/PC-groups, sub/superfields/descriptors, hyperdescriptors and phonetic descriptors must be at level 1.

• Level numbers of fields outside a redefinition must be in the range 1 - 7. See the section ADACMP (COMPRESS-DECOMPRESS) of the Adabas Utilities documentation for a complete description of Adabas levels.

Field Format

The format of the field is indicated in the column F of the Add/Copy/Modify screen. One of the following values can be specified (depending on the file type):

See tables in the section Field Length for valid combinations of format and length.

The following rules apply:

• Any format/length combination is allowed for the file types C (conceptual) or Z (standard).

• For groups, this attribute must be blank.

• For sub/superfields/descriptors in Adabas files, the appropriate format is provided by Predict based on the formats of the fields used. See Rules Applying to Format Changes.

• The following formats are valid for fields within a redefinition: A, B, D, F, I, L, N/U, NS/US, P, PS, T.

Character Set

The parameter Character set determines the format in which data is stored. It is indicated in column Cs of the Add/Copy/Modify screen. The possible values depend on the file type and format.

Character Set - Adabas

The following character set is used to define wide character fields.

Field Length

The field length is indicated in column Length of the Add/Copy/Modify screen. This length is independent of its internal representation. When generating external objects, the field length is adjusted according to the internal representation of data used by the data storage system. For example: a field which is documented with length P9 is implemented with length P5 by the Adabas LOADER utility and the Adabas nucleus.

The following additional rules apply:

Table of Field Formats and Lengths

The table on the following pages contains the valid format/length combinations for fields of the following file types:

Key for the following table

SQL: DBMS Format and Corresponding Predict Format

The table below indicates the DBMS format and the corresponding Predict format for fields in files of the following types:

Key for the following table

Descriptor Type

The descriptor type is indicated in column D of the Add/Copy/Modify screen. The possible values are given in this and the following table.

Additional Information on Descriptor Fields

Descriptor fields can be of various types and control which fields can be used in search criteria (for example in Natural FIND, READ or HISTOGRAM statements). Natural programs can only read Adabas files using fields that are defined as a descriptor (usually type D). It should be part of the design to decide which fields are going to be descriptors, superdescriptors etc.

Adabas however, has a feature where a file can be read using any field - regardless of whether it is a descriptor or not. This is called a non-descriptor search. For large data volumes, this can be very slow. This is because there are no indexes built for non-descriptor fields and a physical scan of the data is required. Despite, if there are only a few records, and it is understood that a physical file scan is taking place, then it can be useful on some occasions.

By putting N into the descriptor type in a DDM, Natural programs are allowed to use this field as a non-descriptor search field. That way you can control in the DDM which fields are allowed to be searched on.

The various descriptor types are documented in more detail in Columns of Field Attributes in the section Using the DDM Editor of the Natural Editors documentation.

Descriptor Type - continued

The following rules apply:

• In an Adabas file, the descriptor must be D if type HM, HP, HQ, HY (all hyperdescriptors), OD (collation descriptor) or PH (phonetic descriptor) is specified.

• For a subdescriptor in an Adabas file, descriptor D and type SB (subfield) must be specified.

• For a superdescriptor in an Adabas file, descriptor D and type SP (superfield) must be specified.

• In a DB2 table or DB2 query table, if a key or index (descriptor D, E, F or P) includes more than one field, the type SP (superfield) must be specified

• In a VSAM file or userview (type L, R, V or W), the descriptor must be either P or A if type SP (superfield) is specified.

• If A is specified for a field of a VSAM file (type L or V), an additional screen is displayed for entering the required definitions (see below).

• Descriptor type must be blank for fields within a redefinition.

Maximum Number of Values / Occurrences

Maximum number of values for a multiple value field or occurrences of a periodic group is indicated in the Occ column of the Add/Copy/Modify screen. This parameter must be specified for multiple value fields and for periodic groups in a redefinition.

When generating Copy Code, the value specified is used as the default for generating the specifications of MU/MC or PE/PC fields in a format buffer and/or record buffer.

When generating ADACMP/ADAFDU definitions, the Occ parameter is evaluated. If Occ is specified, the number of occurrences of each input data record is constant.

If Occ is not specified, the number of occurrences is taken from a counter field preceding a MU/MC or PE/PC field.

See also the section ADACMP (COMPRESS-DECOMPRESS) in the Adabas Utilities documentation.

Unique Option

The unique option is indicated in column U of the Add/Copy/Modify screen. For groups, this attribute must be blank; for other fields, one of the following values can be specified:

Unique option must be blank for fields within a redefinition.

Field Short Name

For file types listed below, the field short name is indicated in the column DB of the Add/Copy/Modify screen. This two-character short name must be defined for the following file types:

A field short name must conform to the rules for coding Adabas field names. See the section ADACMP (COMPRESS-DECOMPRESS) in the Adabas Utilities documentation and Field Names in section Adabas Design of the Adabas Concepts and Facilities documentation.

Field short names for userviews of Adabas, IMS and VSAM files need not be unique.

For fields within a redefinition, parameter Field short name must be blank.

Field short names for SQL tables and views are maintained internally by Predict and cannot be modified by users.

Rotated fields of files of type A (with SQL usage), type AT and B have the same short name and are identified uniquely by an occurrence number (column Occ).

Suppression / Null Value Option

• For fields of Adabas files, the suppression option is indicated in column S of the Add/Copy/Modify screen.

• For fields of SQL files, the null value option is indicated in column N of the Add/Copy/Modify screen.

For groups and for fields within a redefinition, this attribute must be blank. For other fields, one of the following values can be specified:

* See Add/Copy/Modify Screen for SQL Fields for a list of SQL file types.

See also section ADACMP (COMPRESS-DECOMPRESS) in the Adabas Utilities documentation.

Profile Parameter Automatic Null Value

With the profile parameter Automatic null value you can determine an automatic Suppression/Null Value option when fields are added in Predict. See Customizing Predict with Profiles in the section Predict User Interface in the Introduction to Predict documentation.

The value depends on the file type. See table below.

For DB2 fields with Unique option = unique, values R and U are possible.

Variable Length Option - IMS

The variable length option for IMS fields is indicated in column S of the Add/Copy/Modify screen. The following values are valid:

Null Default Option

The NULL default option for fields of SQL tables/views is indicated in the column Df of the Add/Copy/Modify screen. Possible values:

For Ingres fields with format OK or TK, the following additional values are possible:

This parameter must be blank for fields within a redefinition.

Natural Field Length

The Natural field length is indicated in column NAT-l of the Add/Copy/Modify screen. The following rules apply:

• The parameter has to be specified if the field can be:

  • alphanumeric and greater than 253

  • graphic and greater than 126

  • numeric p.q (m/n) where p+q > 29 or q > 7.

    See table of valid formats and lengths in the section Field Length.

• The value specified here is the length that Natural can use for the field as defined in the DDM.

Do Not Convert Option

The "do not convert" option is allowed for A and AV format fields of the following file types:

• Adabas file/userview

• Conceptual file

Related Standard File

This parameter is described in the section Rippling.

Check against standard

This parameter is described in the section Rippling.

Natural Attributes

Headers

The Natural headers 1 - 3 are included in DDMs generated from the file containing the field.

Alphabetic characters in Natural headers are converted to upper-case if the Predict parameter Upper/lower case has been set to Y. See the section Defaults in the Predict Administration documentation.

Index on PE Group Level

If you enter Y in this field and execute the Natural Area Editor command .V for a DDM containing the field object, the maximum occurrences of periodic groups is generated on group level.

If this parameter is left blank (default), the maximum occurrences is generated for each element in the group.

Edit mask

The Natural edit mask. See the description of the DISPLAY statement in the Natural Statements documentation for further details.

Alphabetic characters in the Natural edit mask are converted to upper-case if the Predict parameter Upper/lower case has been set to Y. See the section Defaults in the Predict Administration documentation.

Dynamic length

If you enter Y, fields with format LO or AV in files of type A/U are generated with dynamic length in the DDM.

Hidden

Specifies that the column is not visible in the result for SQL statements unless you explicitly refer to the column by name.

If you enter Y, columns are not visible.

Additional attributes / Associations

The following additional options in the Additional attributes / Associations line are available for fields. Standard options are described in the section Additional attributes / Associations.

Verification

Enter Y in Associations field to call the Predict Link Editor to edit the verification list of the field. Up to 50 verifications can be linked to a field via "Is verified by VE".

This editor can also be invoked by:

• Selecting L (link children with association VE) in the Field Maintenance Menu.

• Entering command LINK ELEMENT VERIFICATION field-id file-id.

See the section Editors in Predict in the Predict Reference documentation.

Additional attributes

Enter Y in this field to define additional attributes. The attributes that can be defined depend on the field type. See Defining Additional Attributes of Fields.