In one embodiment, a process includes determining a data node for a data record to be inserted and/or updated in an index structure of a record-oriented file system. A lock on the corresponding data node is created, and the data record in the corresponding data node is stored and/or updated. However, when the corresponding data node does not have free space sufficient to store and/or update the data record, the corresponding data node is split sequentially into two data nodes. The new data record is stored in one of the two data nodes. The process continues by creating a lock on and updating a parent node in a sequence set which includes information about the corresponding data node and any parent index nodes above the parent index node which are affected by splitting the parent index node.