I was just reading BOL on Recovery Paths (http://msdn.microsoft.com/EN-US/library/02414941-9B9F-4843-9EAC-11DFB7FBFC85(VS.110).aspx
) and they have an example which just doesn't make any sense to me. It's the example where t3 and t4 become obsolete
Imagine a valid transaction inside t3 which adds 'X' to 'table1' which is restored during the PiT restore. Now they do a log backup t5 after some work done and claim that t3 is now obsolete for future recovery.
If I start a recovery, using the full backup t1, followed by t2 + t5, where will value 'X' come from? It was stored inside t3 which is skipped according to their explanation.