Method for checkpointing a main-memory database

A method for making a consistent checkpoint of a computer database in a primary storage to a secondary storage, comprising the steps of:

• beginning checkpointing by identifying a first page in a database to be checkpointed, said first page being on the primary storage and comprising plural data objects, each of said data objects being free of any indication of a pending status concerning any of said data objects being altered subsequent to said first page being identified to be checkpointed;
• altering a first data object of said data objects by way of sub-steps comprising
• i) creating a new data object on said at least one page on said primary storage,
• ii) marking said new data object as pending with a first pending status indicating that said new data object is an updatable copy of said first data object, said new data object marked with said first pending status being accessible to transactions of said computer database,
• iii) marking said first data object with a second pending status indicating that said first data object will be replaced by said new data object with said first pending status after said first data object has been removed,
• iv) moving said first data object marked with said second pending status from said first page to a second page on the primary storage, and
• v) linking said first data object marked with said second pending status with a page identity information including a reference to the first page from which the first data object is moved from said first page in said moving step;
• buffering said first data object marked with said second pending status and said linked page identity information to a first buffer on said primary storage;
• writing said first buffer free of said new data object marked with said first pending status to said secondary storage;
• buffering each of said data objects free of any indication of a pending status to a second buffer on said primary storage to form a buffered contiguous page, said contiguous page being free of said new data object marked with said first pending status;
• writing said second buffer free of said new data object marked with said first pending status to said secondary storage;
• and
• after completing said altering step, replacing said first data object, removed from said first page to said second page, with said new data object in said first page, and, removing said first pending status from said new data object.

A method for making a consistent checkpoint of a computer database in a primary storage to a secondary storage, wherein the method comprises steps of:

• identifying, from within a database management system formed of logical pages of data objects residing on a primary storage (10), one logical page, of the logical pages, to be checkpointed to a secondary storage;
• allocating a physical contiguous area (105a) of the primary storage for the one logical page identified to be checkpointed;
• after identifying the one logical page, modifying one data object of the data objects of the identified one logical page, the modifying of the one data object including providing a pending status marking to the one data object, the pending status marking indicating the modification of the one data object, remaining ones of the data objects of the indentified one logical page being free of any pending status marking indicating modification of the remaining data objects;
• selecting at least the remaining ones of the data objects of the identified one logical page, and copying the selected data objects to the allocated physical contiguous area to form a contiguous page of the selected data objects of the one logical page within the physical contiguous area of the primary storage;
• and
• after said copying step, writing the contiguous page of the selected data objects from the physical contiguous area of the primary storage to the secondary storage to checkpoint the one logical page to the secondary storage.