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Conservative 2PL is completely different from Rigirous 2PL. In conservative 2PL there's no growing phase i.e locks are obtained before the transaction begins. Hence it is free from deadlock. And locks are released one by one in shrinking phase.

In Rigirous 2PL, growing phase is present. But there's no shrinking phase. All locks are released only after the transaction commits. hence it is free from cascading rollback.

Timestamp protocols are free from both.

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In conservation 2PL , transaction need to acquire all the locks before it starts execution by maintaining both READ and WRITE list and Releasing all the locks is performed after commit.

In rigorous 2PL, all locks (Shared and exclusive) are held until it commits.

So we can say, conservation 2PL is also a rigorous 2PL.

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