A system and method for continually updating a large and substantially continually changing dataset that is accessed by multiple application threads, such as a group identity database of members in communication groups of wireless communication devices. A first server holds the group identity database and, as application threads on the first server access the database to set up group communications, a second server sends new group identity data to update the database, with the new data arriving as discrete, ordered blocks. A first server-resident data-index table is updated with the ordering information of the new data blocks, and a first server-resident checkpointing thread places the ordering information of the new data blocks into a checkpoint cache and checkpoints the ordering information as the new data blocks are updated into the group identity database and verifies the ordering (or version) of the data as against the data-index table.