Data area in AS400

Data Area

Data Area is an object which is used to hold data for access by any job running on the AS400 system. You can store a limited size of data in the data area.

We can journal data areas which allow us to recover data area objects to their consistent state if any issue occurs.

Use of Data Area

To provide storage to pass information within a job.
To provide a field that is frequently changed such as any next number whether its order number or check number or user number etc.
To provide a constant field to be used by several jobs such as library name or any flag etc.
To provide limited access to a large process. A data area can be locked by a single user, therefore, preventing others from processing at the same time.

Create Data Area

Use command CRTDTAARA to create a data area other than a local or a group data area. You create a separate object in a library and you can initialize it to a default value.

                         Create Data Area (CRTDTAARA)                         
                                                                              
Type choices, press Enter.                                                    
                                                                              
Data area  . . . . . . . . . . . > DTARA1        Name                         
  Library  . . . . . . . . . . . >   EASYCLASS1  Name, *CURLIB                
Type . . . . . . . . . . . . . . > *CHAR         *DEC, *CHAR, *LGL, *DDM      
Length:                                                                       
  Length . . . . . . . . . . . . > 2000          1-2000                       
  Decimal positions  . . . . . .                 0-9                          
Initial value  . . . . . . . . . > TEST                                       
Text 'description' . . . . . . . > 'Test Data Area'                           
                                                                              
                                                                              
                           Additional Parameters                              
                                                                              
Authority  . . . . . . . . . . .   *LIBCRTAUT    Name, *LIBCRTAUT, *CHANGE...

The data area is created successfully.

Data area DTARA1 created in library EASYCLASS1.

WRKOBJ EASYCLASS1/DTARA1

                              Work with Objects                              
                                                                             
Type options, press Enter.                                                   
  2=Edit authority        3=Copy   4=Delete   5=Display authority   7=Rename 
  8=Display description   13=Change description                              
                                                                             
Opt  Object      Type      Library     Attribute   Text                      
     DTARA1      *DTAARA   EASYCLASS1              Test Data Area

The data area can be of Type character(*CHAR), decimal(*DEC), Logical(*LGL), and remote data area(*DDM).

The Default Length for the Decimal data area is (15,5) and the maximum length for the decimal data area is (24,9).

The Default Length for the character data area is 32 and the maximum length for the character data area is 2000.

The Default and maximum Length for the Logical data area are 1.

A logical data area contains the value of '0' or '1', where '0' means off, false, or no and '1' means on, true, or yes.

When you create the data area you can specify the initial value. If you do not specify the default values would be 0 for decimal, blanks for the character, '0' for logical data area.

Retrieve Data Area value in CL program

Use command RTVDTAARA to retrieve data area value in CL program variable.

Retrieve all the data from the data area.

                         Retrieve Data Area (RTVDTAARA)                 
                                                                        
 Type choices, press Enter.                                             
                                                                        
 Label  . . . . . . . . . . . . .                                       
 Data area specification:         DTAARA                                
   Data area  . . . . . . . . . .              > DTARA1                 
     Library  . . . . . . . . . .              >   EASYCLASS1           
   Substring specifications:                                            
   Substring starting position  .              > *ALL                   
   Substring length . . . . . . .                                       
 CL variable for returned value   RTNVAR       > &VALUE                 
 Comment  . . . . . . . . . . . .

Retrieve substring of data from the data area.

                        Retrieve Data Area (RTVDTAARA)               
                                                                     
Type choices, press Enter.                                           
                                                                     
Label  . . . . . . . . . . . . .                                     
Data area specification:         DTAARA                              
  Data area  . . . . . . . . . .              > DTARA1               
    Library  . . . . . . . . . .              >   EASYCLASS1         
  Substring specifications:                                          
  Substring starting position  .              > 5                    
  Substring length . . . . . . .                5                    
CL variable for returned value   RTNVAR       > &VALUE               
Comment  . . . . . . . . . . . .

Change Data area

Use command CHGDTAARA to change the contents of the data area.

Change All the content of the data area

                         Change Data Area (CHGDTAARA)                   
                                                                        
Type choices, press Enter.                                              
                                                                        
Data area specification:         DTAARA                                 
  Data area  . . . . . . . . . .              > DTARA1                  
    Library  . . . . . . . . . .              >   EASYCLASS1            
  Substring specifications:                                             
  Substring starting position  .                *ALL                    
  Substring length . . . . . . .                                        
New value  . . . . . . . . . . . VALUE        > 'HELLO'

Change substring content of the data area

                         Change Data Area (CHGDTAARA)                    
                                                                         
Type choices, press Enter.                                               
                                                                         
Data area specification:         DTAARA                                  
  Data area  . . . . . . . . . .              > DTARA1                   
    Library  . . . . . . . . . .              >   EASYCLASS1             
  Substring specifications:                                              
  Substring starting position  .              > 2                        
  Substring length . . . . . . .              > 4                        
New value  . . . . . . . . . . . VALUE        > 'CHG1'

Display Data area

Use command DSPDTAARA to display the current value of the data area.

                         Display Data Area (DSPDTAARA)      
                                                            
Type choices, press Enter.                                  
                                                            
Data area  . . . . . . . . . . . DTAARA       > DTARA1      
  Library  . . . . . . . . . . .              >   EASYCLASS1
Output . . . . . . . . . . . . . OUTPUT         *           
Output format  . . . . . . . . . OUTFMT         *CHAR       
                                                            
                           Additional Parameters            
                                                            
System . . . . . . . . . . . . . SYSTEM         *LCL

Press ENTER to display the content of the data area after entering the above DSPDTAARA command.

                               Display Data Area                  
                                                             System
 Data area . . . . . . . :   DTARA1                               
   Library . . . . . . . :     EASYCLASS1                         
 Type  . . . . . . . . . :   *CHAR                                
 Length  . . . . . . . . :   2000                                 
 Text  . . . . . . . . . :   Test Data Area                       
                                                                  
            Value                                                 
 Offset      *...+....1....+....2....+....3....+....4....+....5   
     0      'TEST                                              '  
    50      '                                                  '  
   100      '                                                  '  
   150      '                                                  '  
   200      '                                                  '  
   250      '                                                  '  
   300      '                                                  '  
   350      '                                                  '  
   400      '                                                  '  
                                                                  
 Press Enter to continue.

Delete Data area

Use command DLTDTAARA to delete the data area object.

                         Delete Data Area (DLTDTAARA)        
                                                             
Type choices, press Enter.                                   
                                                             
Data area  . . . . . . . . . . . DTAARA       > DTARA1       
  Library  . . . . . . . . . . .              >   EASYCLASS1

Data area object deleted successfully.

 Selection or command                             
 ===>                                             
                                                  
 F3=Exit   F4=Prompt   F9=Retrieve   F12=Cancel   
 F23=Set initial menu                             
 Object DTARA1 in EASYCLASS1 type *DTAARA deleted.

Data Area Locking and Allocation

CHGDTAARA command uses a *SHRUPD (Shared for Update) lock on the data area during command processing.

RTVDTAARA and DSPDTAARA command uses an *SHRRD (Shared for Reading) lock on the data area during command processing.

If you want to perform more than one operation on the data area, you can use Allocate Object (ALCOBJ) command to prevent others from accessing the data area until your operations are completed. For example, reading a value from a data area and increment it by some value at the same time.

Remote Data Area

Read about Remote Data Area from the following article

Remote Data Area in AS400

Local Data Area

Read about Local Data Area from the following article

Local Data Area in AS400

Group Data Area

Read about group Data Area from the following article

Group Data Area in AS400

Program Initialization Parameter Data Area

Read about Program Initialization Parameter Data Area from the following article

Program Initialization Parameter Data Area in AS400

AS400 and SQL Tricks