Timestamp Ordering Protocol

Question

Suppose that transaction Ti issues write(Q). According to timestamp Ordering protocol:

If TS(Ti)<R-timestamp(Q) then Ti will rollback.

My doubt is if TS(Ti) < R-timestamp(Q),it means write operation is occurring before the read operation and hence the transaction is reading the correct value of Q.Then why is it rolling back? Please correct me where am I going wrong.

Comments

if there are some abort operation, then transaction roll back

Only writing and reading not a cause for roll back

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Oh yes.sorry missed it.Thank you ma'am

Answer 1

There R-timestamp(Q) means process timestamp which read Q value..and it's timestamp is more than the current process which wants to write(Q) so according to timestamp ordering protocol any conflict(hereW-R conflict) from low order timestamp to higher timestamp causes lower timestamp process rollback..so it's (Ti)rollbacked..