Handling Data Areas

• Understanding Data AreasData areas are named permanent storage locations in the IBM i system that can hold several types of data, including character, numeric, or logical values. They are usually defined in a library and are identified by a unique name. The purpose of this storage is to pass information within multiple jobs.The main uses of data area can be:
  • To store job information that is needed to run a group of jobs simultaneously.
  • They are used in auto-generation of numbers e.g., next account no. generation, next invoice no. generation, next order no. generation etc.
• Creating a Data AreaIn CL programming, you can create a data area using the `CRTDTAARA` command.Like:

  CRTDTAARA DTAARA(mylib/mydata) TYPE(*CHAR) LEN(10) VALUE('InitialValue')

  Example:

  

  

• Reading Data from a Data Area With the RTVDTAARA (Retrieve Data Area) command in CL, you can retrieve data from a data area.Example:
  

  

  The Display Data Area (DSPDTAARA) command displays the attributes and value of the specified data area. The following attributes are displayed: the type and length of the data area, the library where the data area is located (there is no library associated with a local data area, the group data area, or the program initialization parameter data area), and the text describing the data area.

  Example:

  

• Writing Data to a Data AreaTo write data to a data area, you can use the `CHGDTAARA` (Change Data Area) command.To change the full Information,
  like:

  CHGDTAARA DTAARA(mylib/mydata) VALUE('NewValue')

  Example:

  

  To change the partial Information, like:

  CHGDTAARA DTAARA(mylib/mydata (Substring starting position       Substring length))
  VALUE('NewValue')

  

  

• Handling Data Area ErrorsHandling data area failures with the MONMSG command is a typical solution in CL programming. When error circumstances are encountered, MONMSG is used to monitor them and execute error-handling methods, allowing for the graceful handling of exceptions connected to data areas.Example:
  

  

• Synchronizing Data AccessIn situations where multiple programs are accessing the same data area simultaneously, you should use synchronization mechanisms, such as locking, to maintain data integrity.
• Cleaning Up Data AreasWhen you no longer need a data area, you can use the `DLTDTAARA` (Delete Data Area) command to remove it from the system.

Like,

DLTDTAARA DTAARA(mylib/mydata)

Example:

Limitations of Data Areas

Handling data areas from CL (Control Language) programming in RPGLE (Report Program Generator) has certain limitations and considerations that you should be aware of to use them effectively. Here are some important restrictions:

• Data Area Size Limitations: The maximum length specified during creation limits the size of data areas. The maximum length depends on the data area type (e.g., *CHAR, *DEC, *LGL ). For instance, a character data area (*CHAR) typically has a maximum length of 2000 characters.
• Limited Data Types: A CL data area can contain only certain types of data, such as character (*CHAR), decimal (*DEC), and logical (*LGL). Besides integer and float types, other data types commonly used in RPGLE are not currently supported.
• No Arrays or Record Formats: There is no support for array or record format structures in data areas. Depending on the type and length of data, they can only hold a single value.
• Limited Error Handling: Error handling in CL is limited compared to RPGLE. MONMSG can be used to monitor for errors during data area operations, but its error handling is less granular than RPGLE’s.