MVCL moves, in fact usually copies, byte strings that are in general more than 256 bytes in length from one storage location to another. It does no serializing. It is indeed interruptible.
CAS is one of a set of serialization instructions, one of which must be used to ensure that two or more CPs do not update a storage location inconsistently.
From the current z/Architecture Principles of Operation:
To ensure successful updating of a common storage field by two or more CPUs, all updates must be done by means of an interlocked-update reference. COMPARE AND SWAP, COMPARE AND SWAP AND PURGE, COMPARE DOUBLE AND SWAP, and TEST AND SET are the only instructions that perform an interlocked-update reference.
John Gilmore SystemCraft LLC
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