9.6.1.0.2 Case 2: $fh_{1a} \in FH_1$ and $fh_{1b} \in FH_1$

Assume $A_1$ is a data access operation using $fh_{1a}$, and $A_2$ is a data access operation using $fh_{1b}$. If for any access $A_1$, there is no access $A_2$ that conflicts with $A_1$, then MPI-/ guarantees sequential consistency.

However, unlike POSIX semantics, the default MPI-/ semantics for conflicting accesses do not guarantee sequential consistency. If $A_1$ and $A_2$ conflict, sequential consistency can be guaranteed by either enabling atomic mode via the MPI_FILE_SET_ATOMICITY routine, or meeting the condition described in Case 3 below.

MPI-Standard for MARMOT