Techniques for increasing the usefulness of transaction logs

Abstract

Techniques for making light-weight checkpoints in logs of streams of transactions and for extending the logs from the checkpoints. The state saved in the light weight checkpoint need only include the state of all transactions that are active at a prior point in the log and are still active at the checkpoint. A log is extended from the checkpoint by processing new transactions in the transaction stream beginning at the prior point to produce the extending log. When the checkpoint is reached, the state saved at the checkpoint is used to continue to produce the extending log. Techniques are further disclosed for selecting points in the stream of transactions at which the checkpoints may be made and for determining the distance between checkpoints. As disclosed, the log in which the checkpoints are used is a logical log made from a physical log produced by a relational database system. The logical log may be used for replication and for data mining.

What is claimed is: 
     
         1 . A computer-implemented method for implementing a transaction log, comprising:
 storing transaction information in the transaction log, wherein the transaction information includes information for both a longer running transaction and a shorter running transaction; and   generating a first set of information corresponding to the longer running transaction and a second set of information corresponding to the shorter running transaction, wherein a level of state information is different between the first set of information and the second set of information, and wherein the level of state information is relatively greater for the first set of information corresponding to the longer running transaction than the second set of information corresponding to the shorter running transactions.   
     
     
         2 . The method of  claim 1 , wherein the transaction log comprises both physical and logical logs. 
     
     
         3 . The method of  claim 2 , wherein the physical log comprises a sequence of redo log blocks and the logical log comprises grouped transaction information and state information. 
     
     
         4 . The method of  claim 2 , wherein the longer running transaction is represented in both the logical log and the physical log, and the shorter running transaction is represented in only the physical log. 
     
     
         5 . The method of  claim 1 , wherein the second set of information comprises no state information such that there is no entry in the logical log for state information for the shorter running transaction. 
     
     
         6 . The method of  claim 1 , further comprising:
 using the first set of information for longer running transactions; and   using the second set of information for shorter running transactions.   
     
     
         7 . The method of  claim 1 , wherein the transaction log is produce by a relational database system. 
     
     
         8 . A computer program product comprising a non-transitory computer-readable medium having executable code which, when executed by a processor, performs a process for implementing a transaction log, the process comprising:
 storing transaction information in the transaction log, wherein the transaction information includes information for both a longer running transaction and a shorter running transaction;   generating a first set of information corresponding to the longer running transaction and a second set of information corresponding to the shorter running transaction, wherein a level of state information is different between the first set of information and the second set of information, and wherein the level of state information is relatively greater for the first set of information corresponding to the longer running transaction than the second set of information corresponding to the shorter running transactions.   
     
     
         9 . The computer program product of  claim 8 , wherein the transaction log comprises both physical and logical logs. 
     
     
         10 . The computer program product of  claim 9 , wherein the physical log comprises a sequence of redo log blocks and the logical log comprises grouped transaction information and state information. 
     
     
         11 . The computer program product of  claim 9 , wherein the longer running transaction is represented in both the logical log, and the physical log and the shorter running transaction is represented in only the physical log. 
     
     
         12 . The computer program product of  claim 8 , wherein the second set of information comprises no state information such that there is no entry in the logical log for state information for the shorter running transaction. 
     
     
         13 . The computer program product of  claim 8 , further comprising:
 using the first set of information for longer running transactions; and   using the second set of information for shorter running transactions.   
     
     
         14 . The computer program product of  claim 8 , wherein the transaction log is produce by a relational database system. 
     
     
         15 . An apparatus for implementing a transaction log, comprising:
 the transaction log for storing transaction information, wherein the transaction information includes information for both a longer running transaction and a shorter running transaction; and   a processor programmed for:   generating a first set of information corresponding to the longer running transaction and a second set of information corresponding to the shorter running transaction, wherein a level of state information is different between the first set of information and the second set of information, and wherein the level of state information is relatively greater for the first set of information corresponding to the longer running transaction than the second set of information corresponding to the shorter running transactions.   
     
     
         16 . The apparatus of  claim 15 , wherein the transaction log comprises both physical and logical logs. 
     
     
         17 . The apparatus of  claim 16 , wherein the physical log comprises a sequence of redo log blocks and the logical log comprises grouped transaction information and state information. 
     
     
         18 . The apparatus of  claim 16 , wherein the longer running transaction is represented in both the logical log and the physical log, and the shorter running transaction is represented in only the physical log. 
     
     
         19 . The apparatus of  claim 15 , wherein the second set of information comprises no state information such that there is no entry in the logical log for state information for the shorter running transaction. 
     
     
         20 . The apparatus of  claim 15 , wherein the processor is further programmed for:
 using the first set of information for longer running transactions; and   using the second set of information for shorter running transactions.