This function locks an ARY array for use by the current thread. An array can be locked for read-only access or read-write access. Multiple threads can lock an array simultaneously for read-only access, but only one thread can lock an array for read-write access at any one time. Use of any ARY function that may modify any aspect of the array - either the data values stored in the array or the meta-data describing the whole array - will fail with an error unless the thread has locked the array for read-write access. Use of an ARY function that cannot modify the array will fail with an error unless the thread has locked the array (in this case the lock can be either for read-only or read-write access).

If " readonly" is zero (indicating the current thread wants to modify some aspect of the array), this function will report an error if any other thread currently has a lock (read-only or read-write) on the array.

If " readonly" is non-zero (indicating the current thread wants read-only access to the array), this function will report an error only if another thread currently has a read-write lock on the array.

The current thread must unlock the array using datUnlock before it can be locked for use by another thread. All arrays are initially locked by the current thread when they are created or opened. The type of access available to the array (" Read" , " Write" or " Update" ) determines the type of the initial lock. For pre-existing arrays, this is determined by the access mode specified when it is first opened. For new and temporary arrays, the initial lock is always a read-write lock.

aryLock( Ary $\ast$ary, int readonly, int $\ast$status );

• If the version of HDS being used does not support object locking, this function will return without action unless the HDS tuning parameter V4LOCKERROR is set to a non-zero value, in which case an error will be reported.

• An error will be reported if the supplied array is currently locked by another thread.

• The majority of ARY functions will report an error if the array supplied to the function has not been locked for use by the calling thread. The exceptions are the functions that manage these locks - aryLock, datUnlock and aryLocked.

• Attempting to lock an array that is already locked by the current thread will change the type of lock (read-only or read-write) if the lock types differ, but will otherwise have no effect.

ary

readonly

status = int$\ast$ (Given and Returned)