A copy of the old and new state of each row affected by each data modification statement is written to the transaction log. This means that if you begin a transaction by issuing the begin transaction command, realize you have made a mistake, and roll the transaction back, the database is restored to its previous condition.
You cannot roll back changes made on a remote Adaptive Server by means of a remote procedure call (RPC).
However, if select/into bulkcopy database option is set to false, the default mode of writetext does not log the transactions. This prevents the transaction log from filling with the extremely long blocks of data that text, unitext, and image fields may contain. To log changes made with writetext, use the with log option.
There is a more complete discussion of transactions in Chapter 23, “Transactions: Maintaining Data Consistency and Recovery.”