Lecture
In order to be able to perform an individual rollback on the general log, all log entries from this transaction are linked to the reverse list. The beginning of the list for pending transactions is the record of the last database change made by this transaction. For completed transactions (individual rollbacks of which are no longer possible), the beginning of the list is the record of the end of the transaction, which is necessarily pushed into the external log memory. The end of the list is always the first record of a database change made by this transaction. Typically, each record contains a unique transaction identifier so that you can restore a direct list of database change records for a given transaction.
So, an individual transaction rollback (we emphasize again that this is possible only for incomplete transactions) is performed as follows:
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IBM System R — реляционная СУБД
Terms: IBM System R — реляционная СУБД