Multi-version concurrency control on in-memory snapshot store of oracle in-memory database

One or more non-transitory computer-readable media storing instructions for performing a method comprising:

• maintaining, on persistent storage, a database that is accessible to a database server;
• wherein the database includes a first set of data;
• maintaining a second set of data in volatile memory that is accessible to the database server;
• wherein each data item in the second set of data is a copy of a corresponding data item in the first set of data;
• wherein both the first set of data and the second set of data have copies of a particular data item;
• maintaining a bitmap that indicates which data items, in the second set of data, are no longer valid;
• wherein maintaining the bitmap includes responding to an update of the particular data item by
• updating the copy of the particular data item in the first set of data;
• without updating the copy of particular data item in the second set of data, setting a particular bit, in the bitmap, that corresponds to the particular data item, to indicate that the copy of the particular data item in the second set of data is not valid.