When DB2 performs an index or table scan, DB2 will block on a row lock when it comes across an uncommitted row which another transaction has exclusively (X) locked.
With locking, if one thread attempts to acquire a lock that is already held by another thread, the thread will block until the lock becomes available.
使用锁定，如果一个线程试图获取其他线程已经具有的锁定，那么该线程将被阻塞，直到该锁定可用。
3
In fact, when this feature is enabled, and the INSERT operation requires a new or reused block, DB2 will take an exclusive (x) lock on the block in order to add it to the target cell.