Method and apparatus for database update/recovery

A method for updating contents of a database in a system in which said database is constructed of pages which are logical storage locations of data, said system including a current version page table for providing information indicating a correspondence between pages currently updated by a transaction and slots which are physical storage locations of data in the database storage medium wherein currently updated contents of the pages are stored, a backup version page table for providing information indicating a correspondence between the pages of said database and slots forming physical storage locations of data in a database storage medium in which the contents of pages to be recovered are stored and for storing therein a copy of the contents of said current version page table at a checkpoint and a journal file for storing a journal record, comprising the steps of:

• (a) updating contents of at least one page of said database;
• (b) updating contents of said current version page table when contents of a page of said database are updated;
• (c) copying the updated contents of the current version page table into the backup version page table at the checkpoint;
• (d) storing said journal record which is representative of the updated contents of the current version page table into said journal file before completion of a transaction;
• (e) storing a journal record which is representative of a completion of said transaction into said journal field at completion of said transaction;
• and
• (f) restoring the contents of the current version page table based on the backup version page table and the journal file so that the current version page table includes updates of the current version page table due to the page updating of the database, at a system failure;
• wherein a plurality of backup page tables are provided in said non-volatile storage medium at a checkpoint under system operation, said plurality of backup version page tables are cyclically used and selected sequentially as an object to be updated, and the selected backup version page table is updated by storing a copy of the contents of the updated current version page table into said backup version page table.

A method for updating contents of a database in a system in which said database is constructed of pages which are logical storage locations of data, said system including a current version page table for providing information indicating a correspondence between pages currently updated by a transaction and slots which are physical storage locations of data in the database storage medium wherein currently updated contents of the pages are stored, a backup version page table for providing information indicating a correspondence between the pages of said database and slots forming physical storage locations of data in a database storage medium in which the contents of pages to be recovered are stored and for storing therein a copy of the contents of said current version page table at a checkpoint and a journal file for storing a journal record, comprising the steps of:

• (a) updating contents of at least one page of said database;
• (b) updating contents of said current version page table when contents of a page of said database are updated;
• (c) copying the updated contents of the current version page table into the backup version page table at the checkpoint;
• (d) storing said journal record which is representative of the updated contents of the current version page table into said journal file before completion of a transaction;
• (e) storing a journal record which is representative of a completion of said transaction into said journal field at completion of said transaction;
• and
• (f) restoring the contents of the current version page table based on the backup version page table and the journal file so that the current version page table includes updates of the current version page table due to the page updating of the database, at a system failure;
• wherein there is provided a checkpoint dump file for storing system management information in main storage at a checkpoint, and wherein the checkpoint dump file of said current version page table is placed into said checkpoint dump file at a checkpoint, and at the end of system operation said backup version page table in said non-volatile storage medium is updated by storing a copy of the contents of said current version page table to said backup version page table.

A method for updating contents of a database in a system in which said database is constructed of pages which are logical storage locations of data, said system including a current version page table for providing information indicating a correspondence between pages currently updated by a transaction and slots which are physical storage locations of data in the database storage medium wherein currently updated contents of the pages are stored, a backup version page table for providing information indicating a correspondence between the pages of said database and slots forming physical storage locations of data in a database storage medium in which the contents of pages to be recovered are stored and for storing therein a copy of the contents of said current version page table at a checkpoint and a journal file for storing a journal record comprising the steps of:

• (a) storing a journal record which is representative of a completion of a transaction into said journal file at completion of said transaction;
• and
• (b) restoring the content of the current version of the page table based on the backup version of the page table so that the current version of the page table includes updates of the current version of the page table due to the page updating of the database of the system failure;
• wherein at a time of system failure, by fetching journal records from said journal file and analyzing said fetched journal records, a terminal message and updated system management information in a main storage are recovered respectively for complete transactions;
• and by using the journal record representative of the updated contents of said current version page table associated with the database updates produced by a transaction, and said backup version page table, said current version page table is recovered such that only the change of said current version page table associated with the database updates by the complete transactions is restored to said current version table to thereby ensure logical integrity of the database.

A method for updating contents of a database in a system in which said database is constructed of pages which are logical storage locations of data, said system including a current version page table for providing information indicating a correspondence between pages currently updated by a transaction and slots which are physical storage locations of data in the database storage medium wherein currently updated contents of the pages are stored, a backup version page table for providing information indicating a correspondence between the pages of said database and slots forming physical storage locations of data in a database storage medium in which the contents of pages to be recovered are stored and for storing therein a copy of the contents of said current version page table at a checkpoint and a journal file for storing a journal record comprising the steps of:

• (a) storing a journal record which is representative of a completion of a transaction into said journal file at completion of said transaction;
• and
• (b) restoring the content of the current version of the page table based on the backup version of the page table so that the current version of the page table includes updates of the current version of the page table due to the page updating of the database of the system failure;
• wherein a plurality of backup page tables are provided in said non-volatile storage medium at a checkpoint under system operation, said plurality of backup version page tables are cyclically used and selected sequentially as an object to be updated, and the selected backup version page table is updated by storing a copy of the contents of the updated current version page table into said backup version page table.

A method for updating contents of a database in a system in which said database is constructed of pages which are logical storage locations of data, said system including a current version page table for providing information indicating a correspondence between pages currently updated by a transaction and slots which are physical storage locations of data in the database storage medium wherein currently updated contents of the pages are stored, a backup version page table for providing information indicating a correspondence between the pages of said database and slots forming physical storage locations of data in a database storage medium in which the contents of pages to be recovered are stored and for storing therein a copy of the contents of said current version page table at a checkpoint and a journal file for storing a journal record comprising the steps of:

• (a) storing a journal record which is representative of a completion of a transaction into said journal file at completion of said transaction;
• and
• (b) restoring the content of the current version of the page table based on the backup version of the page table so that the current version of the page table includes updates of the current version of the page table due to the page updating of the database of the system failure;
• wherein there is provided a checkpoint dump file for storing system management information in a main storage at a checkpoint, and wherein the checkpoint dump file of said current version page table is placed into said checkpoint dump file at a checkpoint, and at the end of system operation said backup version page table in said non-volatile storage medium is updated to store the contents of said current version page table to said backup version page table.