Q. Does Object Manager do any write locks on objects, such as arrays?

A. There is no write locking on scalar objects. The mode flag on the OMfind_subobj API call should serve this purpose, but is not. The mode flag on Object Manager array routines (such as OMret_array_ptr) does do write locking. If the mode flag is set to WR (write) or RW (read-write), the Object Manager will not let you get the array for writing. The array is unlocked when an ARRfree is executed on it. However, since Express is single threaded, this won't generally be an issue. Typically, a module executes, gets the array, frees it when it's done and then returns. Then the next module fires. So there won't normally be any contention.