System and program product for sequential coordination of external database application events with asynchronous internal database events
View Patent ↗Database management systems and program products that exploit time dependent sequential database management system processes to ensure presentation of the same data or view to one or a plurality of users through sequencing asynchronous database management operations such as recovery and replication. Sequencing is accomplished through the use of entries in sequential logs, including transaction logs, recovery logs, and other data recovery tools and applications. Uses include managing data migration and data replication.
1. A database management system that includes a replication system, a processor, and a memory, the database management system comprising:
at least one database table that is subject to replication;
a recovery log;
a replication signal table;
said replication system creates entries in the recovery log in response to changes to a state of any one or more of the at least one database table and the replication signal table, wherein said replication signal table is a specific table that is configured for all users of the database management system, and wherein the entries in the recovery log are ordered with log sequence numbers;
said replication system inserting into the replication signal table a replication command to the replication system relating to the at least one database table and comprising a first log sequence number correlating to a current first recovery log entry;
said replication system detecting a second recovery log entry in the recovery log for said replication command;
said replication system processing recovery log entries that are positioned subsequent to the second recovery log entry according to the log sequence numbers of the recovery log and executing said replication command entered in the replication signal table only after processing all recovery log entries up to the first recovery log entry pointed to by the first log sequence number.
2. The database management system of claim 1 wherein said replication command comprises a second command, and wherein the second command is a signal starting copying into a first database table.
3. The database management system of claim 2 comprising at least two database tables, and the second command is a signal starting copying of contents of the first database table into a second database table.
4. The database management system of claim 1 said replication command comprising a first command that is a signal stopping copying of data into a first database table, and a second command is a signal starting copying of contents of the first database table into a second database table.
5. The database management system of claim 4 , wherein said database management system is configured and controlled for performing an operation on the first database table between the first command and the second command, and thereafter executing the second command.
6. The database management system of claim 5 , wherein said database management system is configured and controlled for changing a schema of the first database table between the first command and the second command, and thereafter executing the second command.
7. The database management system of claim 1 wherein a first command is a signal stopping copying of data into a first database table, and the second command is a signal reinitializing copying of data into the first database table.
8. The database management system of claim 1 wherein said replication command entered in said replication signal table controls the processing of database events in a same transaction as said replication command.
9. A program product comprising executable program codes stored on a processor usable storage medium and executed by a processor, the program product for managing a database management system, comprising:
said database management system comprising a replication system, at least one database table that is subject to replication, a recovery log, and a replication signal table;
a program code for creating entries in the recovery log in response to changes to a state of any one or more of the at least one database table and the replication signal table, wherein said replication signal table is a specific table that is configured for all users of the database management system, and wherein the entries in the recovery log are ordered with log sequence numbers;
a program code for inserting a replication command to the replication system into the replication signal table, said replication command relating to the at least one database table and comprising a first log sequence number correlating to a current first recovery log entry; and
a program code for detecting a second recovery log entry in the recovery log for the said replication command;
a program code for processing recovery log entries that are positioned subsequent to the second recovery log entry according to the log sequence numbers of the recovery log and executing said replication command entered in the replication signal table only after processing all recovery log entries up to the first recovery log entry pointed to the first log sequence number.
10. The program product of claim 9 wherein said replication command comprises a second command, and wherein the second command is a signal starting copying into a second database table.
11. The program product of claim 10 wherein the database management system comprises at least two database tables, and the second command is a signal starting copying of contents of a first database table into the second database table.
12. The program product of claim 11 , said replication command comprising a first command that is a signal stopping copying of data into the first database table.
13. The program product of claim 12 wherein the second command is a signal reinitializing copying of data into the second database table.
14. The program product of claim 12 , wherein the database management system is configured and controlled for performing an operation on the first database table between the first command and the second command, and thereafter executing the second command.
15. The program product of claim 14 , wherein the database management system is configured and controlled for changing a schema of the first database table between the first command and the second command, and thereafter executing the second command.
16. The program product of claim 9 , further comprising a program code for ordering database events in sequence using the recovery log.
17. The program product of claim 16 , wherein ordering the database events comprises placing asynchronous database events in sequence.
18. The program product of claim 17 , wherein placing the asynchronous database events in sequence, comprises using the recovery log to place the asynchronous events in sequence between adjacent synchronous events.