How to Create Shared Memory Object Class in ABAP

Create AREA ROOT Class for Shared Memroy Object Area

The first step is to create an Area Rool class. ( let’s say ZCL_ROOT)

Go to SAP Transaction SE24 and create a new class.

Make sure you checked “Shared Memory Enabled” under Class/Interface Propertiess Tab as following:

Create 2 Instance Attributes

The next step is to create, for example, 2 Instance Attributes within this class.
The Visibility has to be set to Private .

Create SET_DATA & GET_DATA Method

Both of these methods SET_DATA and GET_DATA with handle Shared Memory Object Write and Read operation. We will come back to these methods’ implementation later.

Check also How to use EXPORT or IMPORT data to / from ABAP Memory ID

Create SAP Shared Memory Area ( SHMA )

Launch the Transaction SHMA and create a new Area Name. (ZCL_MEM_AREA for sample)
Fill a short description for the Memory Shared Area. In the Root Class, put the class you have created above ( ZCL_ROOT ).

When saving, SAP will generate an area Class with the same name as the Area Name ( ZCL_MEM_AREA ). The new generated Area Class will contains all the methods needed to read, write and update the Shared Memory Object.

Shared Memory Object Area Class’s Methods

[table tablesorter=”o” class=”table table-border” id=”Shared Memory Area Class Methods”]
Method, Visibility, Description
ATTACH_FOR_READ,Public,Request a Read Lock
ATTACH_FOR_UPDATE,Public,Request a Change Lock
ATTACH_FOR_WRITE,Public,Request a Write Lock
BUILD, Static, Direct Call of Area Constructor
SET_ROOT, Instanciate, Sets Root Objects
[/table]

SET_DATA and GET_DATA Implementation

Once you have created the area root class, the area class and generated the area class, you can implement the ABAP code for the SET_DATA and GET_DATA in order to read/Write the Shard Memory Object.

Write data in Shared Memory Area (SET_DATA)

In order to save data into an instance of Shared Memory Object, you can set the data as following :

    DATA: my_handle TYPE REF TO zcl_mem_area.
    DATA: my_root   TYPE REF TO zcl_area_root.

    TRY .

        CALL METHOD zcl_mem_area=>attach_for_write
          EXPORTING
            inst_name   = cl_shm_area=>default_instance
            attach_mode = cl_shm_area=>attach_mode_default
            wait_time   = 0
          RECEIVING
            handle      = my_handle.

        CREATE OBJECT my_root AREA HANDLE my_handle.

        CALL METHOD my_root->set_data
          EXPORTING
            name  = 'name_test'
            value = 'value_test'.

        CALL METHOD my_handle->detach_commit.

      CATCH cx_shm_exclusive_lock_active .
      CATCH cx_shm_version_limit_exceeded .
      CATCH cx_shm_change_lock_active .
      CATCH cx_shm_parameter_error .
      CATCH cx_shm_pending_lock_removed .

    ENDTRY.

Read data in Shared Memory Area (GET_DATA)

here an example how to use the GET_DATA in order to read an instance of Shared Memory Object:

    DATA: my_handle TYPE REF TO zcl_mem_area.
    DATA: my_root   TYPE REF TO zcl_area_root.


    TRY .

        CALL METHOD zcl_mem_area=>attach_for_read
          EXPORTING
            inst_name = zcl_mem_area=>attach_for_write
          RECEIVING
            handle    = my_handle.

        CREATE OBJECT my_root AREA HANDLE my_handle.

        CALL METHOD my_root->get_data
          IMPORTING
            name  = lv_name
            value = lv_value.

        CALL METHOD my_handle->detach_commit.

       CATCH cx_shm_inconsistent .
       CATCH cx_shm_no_active_version .
       CATCH cx_shm_read_lock_active .
       CATCH cx_shm_exclusive_lock_active .
       CATCH cx_shm_parameter_error .
       CATCH cx_shm_change_lock_active .

    ENDTRY.

Note that NAME and VALUE are the attribute of the Area Root Class.

List of Area Root Class Exception

Here the list of the main exception Class for Area Root:
[table tablesorter=”o” class=”table table-border”
CX_SHM_INCONSISTENT,Different Definitions Between Program and Area
CX_SHM_NO_ACTIVE_VERSION,No active version exists for an attach
CX_SHM_READ_LOCK_ACTIVE,Request for a Second Read Lock
CX_SHM_EXCLUSIVE_LOCK_ACTIVE,Instance Already Locked
CX_SHM_PARAMETER_ERROR,Incorrect parameter transferred
CX_SHM_CHANGE_LOCK_ACTIVE,A Change Lock Is Already Active
CX_SHM_EXCLUSIVE_LOCK_ACTIVE,Instance Already Locked
CX_SHM_VERSION_LIMIT_EXCEEDED,No Additional Versions Available
CX_SHM_CHANGE_LOCK_ACTIVE,A write lock is already active
CX_SHM_PARAMETER_ERROR,Passed Parameter Has Incorrect Value
CX_SHM_PENDING_LOCK_REMOVED,Shared Objects: Waiting Lock Was Deleted
[/table]