How is a Transaction ID generated & when does it change? (with a new sequence ID?) I'm creating a non-mainstream client that processes and validates Bitcoin transactions and need to track transactions in my database.


How is the TxID generated and when does it change?  


Specifically, since sequence is intended to update a transaction, and if the transactions hash were to change I would assume the txid hash would change s well.

When I look at this image of a Tx, it appears that the txid is marked as TxIn (VI) 


Is it possible or useful for a script to verify the TxID and signature hash?
TxID is just a SHA256 hash of binary transation data, so it changes upon any modification of transaction.
Therefore, one cannot include verification of TxID in the script in same transaction (if I correctly understood what you want to achieve).