ons must also have a way of recalling swapped blocks when they are needed.</P>
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These requirements are met by the memory manager's locking scheme. Whenever you need to access data in a non-fixed block, you must first lock it. This will cause the memory manager to copy the block back into the global heap if it had been swapped; the memory manager will not move, swap, or discard a block while the block is locked.</P>
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Any block may be locked several times. Each lock increments the block's lock count (to