#include <ShoreApp.h> shrc REF(T)::valid(LockMode lm = SH) const;
The valid method indicates whether the given ref can be followed safely. In this context, "safe" means that there is an object at the other end of the ref, and that the object can be locked in the indicated lock mode. This method will obtain the lock, but will not fetch the object into the object cache. The fetch method can be used for this purpose.
A return code of RCOK indicates that the lock was successfully obtained, and that the ref is therefore valid. Any other error code indicates either that the ref is not valid, or that the lock could not be obtained (perhaps due to insufficient permission on the part of the process).
Because this method obtains a lock on the object, it may be forced to wait, in another transaction holds a conflicting lock on the object.
It is legal, and potentially useful, to pass a lock mode of NL (no lock) to valid. However, if no lock is obtained, then nothing prevents another transaction from destroying the referenced object, thereby invalidating the ref, before the end of the current transaction.