Each user session can contain one or more ABAP sessions. Each ABAP session is allocated its own ABAP memory area where clusters of data can be stored. Programs calling the sequence share access to these clusters.
A new ABAP session can be opened in the same user session as follows:
- Enter the transaction code after "/o" in the command field in the toolbar.
- Call the function module TH_CREATE_MODE.
- dynpro is called when processing an asynchronous RFC. For this, the RFC client needs an additional ABAP session to communicate with the SAP GUI.
Each user session can have up to 16 ABAP sessions. The actual number of possible sessions for the system is determined by the configuration file parameter rdisp/max_alt_modes, which defaults to 6.
The following figure is a screenshot of the RZ11 transaction code on the author's ABAP system to open the above parameters:
Each call to an ABAP program creates a new internal session in which the called program is loaded.
The memory area for internal sessions is called poll area, which itself is divided into heap and stack areas. This is where the modifiable objects of the program are kept. Unmodifiable program data is stored in the PXA. The poll area contains references to the necessary data in PXA. Technically, the poll area and global PXA are stored in the shared memory of the application server, which is the responsibility of SAP memory management.
In an ABAP session, there can be up to nine internal sessions, which always belong to a call sequence (that is, a call sequence). Data in ABAP memory is always allocated to a call sequence.
On 64-bit platforms, an internal session theoretically requires up to 4 TB of memory. On 32-bit platforms, the theoretical upper limit is 4 GB. The actual limit is usually lower than the theoretical limit, because the actual installed main memory is the maximum available and is distributed among all consuming programs.
A call sequence is a set of programs whose internal sessions are loaded together in an ABAP session through a call sequence using SUBMIT … AND RETURN or CALL TRANSACTION.