Justification of shared memory way of use

Hi,

According to SAP, shared memory object is supposed to be changed infrequently, about one time in an hour or even less frequently. SAP says, "You should not use shared memory for different purposes if, for example, this results in many modifying accesses of parallel users, as the current locking concept does not support this."
Can you guys clarify what that means? There is a locking mechanism but it takes an hour to recover after a modification happens? Perhaps the reason is because a process can change an SHM object once it gets a direct access, while some other process following locking logic doesn't know that the first process is changing this object?

THanks!