Method and means for archiving modifiable pages in a log based transaction management system

Claim 1

A method for archiving a file of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, said file having a header page, status page (SMP), and at least one data page, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page -- LSN being recorded on the page, comprising the steps of: (a) creating and maintaining a first global log sequence number (ICBU -- LSN) on said header page and a plurality of status bits (ICB) on said SMP, each ICB being counterpart to each of the data pages and indicative of the page having been modified since an immediately prior archive or copy operation; (b) setting the ICBU -- LSN to a maximum value, and establishing a second global log sequence number (ICRF -- LSN) and recording said ICRF -- LSN in a system catalog; (c) ascertaining a set of pages subject to archiving by scanning the ICBs in the SMP and resetting that subset of ICBs indicative of the pages having been modified since an immediately prior archive or copy operation; (d) executing a copy operation by in turn latching, copying, and unlatching each page of said subset of ICBs scanned and reset in step (c) for incremental copying and for all pages irrespective of their ICB condition for full copying; (e) setting the ICBU -- LSN to the current end -- of -- log -- LSN value and recording it in the header page; and (f) responsive to each page modification, setting the counterpart ICB in the SMP if the page -- LSN<ICBU -- LSN, and recording the action in the log with a REDO only log record.

Claim 2

A method for archiving a file of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, said file having a header page, status page (SMP), and at least one data page, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page -- LSN being recorded on the page, comprising the steps of: (a) creating and maintaining a first global log sequence number (ICBU -- LSN) on said header page and a plurality of status bits (ICB) on said SMP, each ICB being counterpart to each of the data pages and indicative of the page having been modified since an immediately prior archive or copy operation; (b) setting the ICBU -- LSN to a maximum value, and establishing a second global log sequence number (ICRF -- LSN) and recording said ICRF -- LSN in a system catalog; (c) ascertaining a set of pages subject to archiving by scanning the ICBs in the SMP and resetting that subset of ICBs indicative of the pages having been modified since an immediately prior archive or copy operation; (d) executing a copy operation by in turn latching, copying, and unlatching each page of said subset of ICBs scanned and reset in step (c) for incremental copying and for all pages irrespective of their ICB condition for full copying; (e) setting the ICBU -- LSN to the current end -- of -- log -- LSN value and recording it in the header page; and (f) responsive to each page modification, setting the counterpart ICB in the SMP if the page -- LSN<ICBU -- LSN, and recording the action in the log with a REDO only log record.

Claim 6

A method for archiving a database of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page -- LSN being recorded on the page, comprising the steps of: (a) initializing a copy operation for a partition of the database by (1) invoking a database control block (DBCB) for said partition, said partition having a header page, at least one data page, and at least one space map page (SMP) including a status bit (ICB) for each data page indicative as to whether the data page has been modified since execution of a prior copy operation, (2) atomically setting an LSN of a first kind (ICBU -- LSN) to a maximum value in the DBCB, setting an LSN of a second kind (ICRF -- LSN) to a value set by the current end -- of -- log LSN, and recording the ICRF -- LSN in a system catalog, and (3) ascertaining the set of data page's subject to copying for each SMP by resetting all ICB's of data pages indicative of being updated since the last copy operation and recording all of the ICB's so reset in the log; and (b) executing said copy operation by (1) for each SMP, latching, copying, and unlatching each data page identified in step (a)(3), and (2) updating the ICBU -- LSN in the DBCB and the header page to the current end -- of -- log LSN value, (3) committing the operation, and (c) responsive to each page modification, setting the counterpart ICB in the status page if the page -- LSN<ICBU -- LSN and record the action in the log.

Claim 7

A method for archiving a database of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page -- LSN being recorded on the page, comprising the steps of: (a) initializing a copy operation for a partition of the database by (1) invoking a database control block (DBCB) for said partition, said partition having a header page, at least one data page, and at least one space map page (SMP) including a status bit (ICB) for each data page indicative as to whether the data page has been modified since execution of a prior copy operation, (2) atomically setting an LSN of a first kind (ICBU -- LSN) to a maximum value in the DBCB, setting an LSN of a second kind (ICRF -- LSN) to a value set by the current end -- of -- log LSN, and recording the ICRF -- LSN in a system catalog, and (3) ascertaining the set of data page's subject to copying for each SMP by resetting all ICB's of data pages indicative of being updated since the last copy operation and recording all of the ICB's so reset in the log; and (b) executing said copy operation by (1) for each SMP, latching, copying, and unlatching each data page identified in step (a)(3), and (2) updating the ICBU -- LSN in the DBCB and the header page to the current end -- of -- log LSN value, (3) committing the operation, and (c) responsive to each page modification, setting the counterpart ICB in the status page if the page -- LSN<ICBU -- LSN and record the action in the log.

Claim 8

A method for archiving a file of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, said file having a header page, status page (SMP), and at least one data page, each page in the file has recorded thereon an ascending page number independent of any other indicia, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page LSN being recorded on the page, comprising the steps of: (a) creating and maintaining a first global log sequence number (ICBU -- LSN) on said header page and a plurality of status bits (ICB) on said SMP, each ICB being counterpart to each of the data pages and indicative of having been modified since an immediately prior archive or copy operation; (b) setting the ICBU -- LSN to a maximum value, and establishing a second global log sequence number (ICRF -- LSN) and recording said ICRF -- LSN in a system catalog, said system catalog comprising entries recording information about each full or incremental copy of the file, each entry including a pointer to the location of each archive copy of the file in the storage subsystem and an ICRF -- LSN set to an end -- of -- log -- LSN, (c) ascertaining a set of pages subject to archiving by scanning the ICBs in the SMP and resetting that subset of ICBs indicative of the pages having been modified since an immediately prior archive or copy operation; (d) executing a copy operation by in turn latching, copying, and unlatching each page of said subset of ICBs scanned and reset in step (c) for incremental copying and for all pages irrespective of their ICB condition for full copying; (e) setting the ICBU -- LSN to the current end -- of -- log -- LSN value and recording it in the header page; (f) responsive to each page modification, setting the counterpart ICB in the SMP if the page -- LSN<ICBU -- LSN, and recording the action in the log with a REDO only log record; (g) making a full copy of each file each time the data is loaded into the file without logging, suspending any data page modifications until the full copy is made, and recording the pointer location, copy type (full) and ICRF -- LSN in the system catalog; (h) making incremental or full copies of each file on a scheduled or opportunistic basis including entries to the system catalog; and (i) responsive to the unavailability of a file in the external storage subsystem, recovering said file by merging according to their page numbers the contents of the full and incremental copies as defined by the system catalog, and modifying the merged page set according to the log records having an LSN equal to or greater than the ICRF -- LSN.

Claim 9

A method for archiving a file of modifiable pages in a phased commit transaction management system (TMS) having a log, a processor, and a storage subsystem in which pages stored therein are staged to and from the processor, said file having a header page, status page (SMP), and at least one data page, each page in the file has recorded thereon an ascending page number independent of any other indicia, the processor being responsive to each transaction and executing selective modifications to predetermined ones of the pages, each modification to a page state being recorded in the log and assigned an ascending log sequence number (page -- LSN), said page LSN being recorded on the page, comprising the steps of: (a) creating and maintaining a first global log sequence number (ICBU -- LSN) on said header page and a plurality of status bits (ICB) on said SMP, each ICB being counterpart to each of the data pages and indicative of having been modified since an immediately prior archive or copy operation; (b) setting the ICBU -- LSN to a maximum value, and establishing a second global log sequence number (ICRF -- LSN) and recording said ICRF -- LSN in a system catalog, said system catalog comprising entries recording information about each full or incremental copy of the file, each entry including a pointer to the location of each archive copy of the file in the storage subsystem and an ICRF -- LSN set to an end -- of -- log -- LSN, (c) ascertaining a set of pages subject to archiving by scanning the ICBs in the SMP and resetting that subset of ICBs indicative of the pages having been modified since an immediately prior archive or copy operation; (d) executing a copy operation by in turn latching, copying, and unlatching each page of said subset of ICBs scanned and reset in step (c) for incremental copying and for all pages irrespective of their ICB condition for full copying; (e) setting the ICBU -- LSN to the current end -- of -- log -- LSN value and recording it in the header page; (f) responsive to each page modification, setting the counterpart ICB in the SMP if the page -- LSN<ICBU -- LSN, and recording the action in the log with a REDO only log record; (g) making a full copy of each file each time the data is loaded into the file without logging, suspending any data page modifications until the full copy is made, and recording the pointer location, copy type (full) and ICRF -- LSN in the system catalog; (h) making incremental or full copies of each file on a scheduled or opportunistic basis including entries to the system catalog; and (i) responsive to the unavailability of a file in the external storage subsystem, recovering said file by merging according to their page numbers the contents of the full and incremental copies as defined by the system catalog, and modifying the merged page set according to the log records having an LSN equal to or greater than the ICRF -- LSN.