Journaling database changes using a bit map for zones defined in each page

Abstract

The disclosure and claims herein are directed to efficient journaling for recovery of a database index by journaling zones of a page. A journal mechanism maintains a page zone bit map that includes a bit for a plurality of zones in each page to indicate which zones have had their unchanged image journaled before being changed since a last sync point update. The page zone bit map has a bit for each zone in each page so that the status of each zone can be tracked separately. Tracking the smaller zones of the pages makes the process more efficient both at run time and during recovery by reducing the period of time for memory deposits and reducing the amount of total redundant/recovery data sent to disk for larger pages.

1 . An apparatus comprising:
 at least one processor;   a memory coupled to the at least one processor;   a database residing in the memory, the database comprising a plurality of pages that are each divided into a plurality of zones;   a paging mechanism for storing the pages from memory to an auxiliary storage;   a page zone bit map residing in the memory including a plurality of bits corresponding to one of the plurality of pages, each bit in the page zone bit map corresponding to one of the plurality of zones in the corresponding one page, wherein a state of a bit in the page zone bit map indicates whether any changes have been made to the one corresponding zone; and   a journaling mechanism that tracks changes to the plurality of zones in the plurality of pages by changing the state of the plurality of bits to journal a changed zone in a page.   
     
     
         2 . The apparatus of  claim 1  wherein the page zone bit map comprises a page bit map with a bit for each page and a zone bit map with a bit for each zone in each page. 
     
     
         3 . The apparatus of  claim 2  wherein the journal mechanism uses the bit corresponding to the page bit map to indicate that a bit in the zone bit map is set, and the journaling mechanism uses the bit in the zone bit map to indicate which zones have had their unchanged image journaled before being changed since a last sync point update. 
     
     
         4 . The apparatus of  claim 1  wherein the journaling mechanism uses the bit in the page zone bit map to indicate which zones have had their unchanged image journaled before being changed since a last sync point update. 
     
     
         5 . The apparatus of  claim 1  wherein the journaling mechanism waits to journal zones with virgin states until the first time the zones are modified. 
     
     
         6 . A computer-implemented method for journaling zones of a leaf page for a database index, the method comprising the steps of:
 (A) providing a database with a plurality of pages divided into a plurality of zones;   (B) providing a page zone bit map including a plurality of bits corresponding to one of the plurality of pages, each bit in the page zone bit map corresponding to one of the plurality of zones in the corresponding one page, wherein a state of a bit in the page zone bit map indicates whether any changes have been made to the one corresponding zone; and   (C) journaling the database using a bit in the page zone bit map to indicate which zones have had their unchanged image stored to the database journal.   
     
     
         7 . The method of  claim 6  wherein the page zone bit map further comprises a page bit map with a bit for each page and a zone bit map with a bit for each zone in each page. 
     
     
         8 . The method of  claim 7  further comprising the steps of:
 using the bit corresponding to the page bit map to indicate that a bit in the zone bit map is set, and 
 using the bit in the zone bit map to indicate which zones have had their unchanged image journaled before being changed since a last sync point update. 
 
     
     
         9 . The method of  claim 7  further comprising the step of waiting to journal zones with virgin states until the first time the zones are modified.