SAP FILE INTERFACE LOCKING

Get Example source ABAP code based on a different SAP table
  SAP Help

Locking Files
The file interface does not contain an integrated locking mechanism that ensures that only one ABAP program at a time can access a file. If multiple programs are writing to a file at the same time, the results are unpredictable.
To avoid this situation, SAP locks or an unambiguous file name, such as UUIDs should be used.



Latest notes:
When multiple ABAP_ASINSTANCES in AS ABAP try to access a file at the same time, conflicts can still occur despite SAP locks. This is the case, for example, when the operating system buffers data before writing it to a file.
ABAP_HINT_END