Provided are a computer program product, system, and method for generating node access information for a transaction accessing nodes of a data set index. Pages in the memory are allocated to internal nodes and leaf nodes of a tree data structure representing all or a portion of a data set index for the data set. A transaction is processed with respect to the data set that involves accessing the internal and leaf nodes in the tree data structure, wherein the transaction comprises a read or write operation. Node access information is generated in transaction information, for accessed nodes comprising nodes in the tree data structure accessed as part of processing the transaction. The node access information includes a pointer to the page allocated to the accessed node prior to the transaction in response to the node being modified during the transaction.