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Logical State

• Orec defines a unique logical state of a heap location

Orec contains	Logical State
Version number (always odd)	Value from the heap, version from orec
Pointer to transaction, which contains entry for this address	If transaction committed: new value/version, else: old value/version
Pointer to transaction with no entry for this address	One orec serving multiple memory locations: use value from the heap, version from another entry mapped to the same orec

Consistent snapshot guaranteed by:

 do {
    orec := orec_of (addr);
    directly compute logical state based on orec
 } while (orec_of (addr) != orec);

• Orecs contain pointer only when a tranasction is committing
• Logical value changes atomically with the change of transaction status
• Undefined when transaction in READ-CHECK state. Possible reaction: help or kill.

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