Oracle International Corporation

Lei Gao

Lik Wong

Nimar Singh Arora

Anand Lakshminath

Thuvan Hoang

Alan Robert Downing

Ramkumar Venkatesan

Byron Wang

Jun Yuan

Patricia H McElroy

Cristina Schmidt

Haobo Xu

Jingwei Wu

Thuyan Hoang

A method for sharing information between a publisher and multiple subscribers is provided. The publisher uses a latch-free, single publisher, multiple subscriber shared queue to share information. Logical change records representing changes made to a database are enqueued in the shared queue as messages in a stream of messages, and subscribers read the logical change records. Subscribers may filter logical change records before sending to apply processes for processing. An identifying property of the source instance of a change encapsulated in a logical change record may be included with each message enqueued.

High performant information sharing and replication for single-publisher and multiple-subscriber configuration

Techniques for replicating data between database systems without taking checkpoints are provided. In an embodiment, a capture process restarts. Upon restarting, the capture process reestablishes an association with an apply process. A particular logical time maintained by the apply process is then communicated to the capture process. Upon receiving the particular logical time, the capture process restarts mining from this particular logical time.

Checkpoint-free in log mining for distributed information sharing

In accordance with an embodiment of the present invention, an information sharing mechanism comprising a memory structure may be provided in a database system. In an embodiment, mined information transferred by a capture process to an associated apply process can be written into the memory structure without taking any latch. Similarly, the mined information can be read by the apply process from the memory structure without taking any latch. The capture and apply processes may work cooperatively to establish a safe point in log mining under various circumstances such as in an initial startup state, in a steady state, in a process restart scenario in the middle of information sharing. In some embodiments, the information sharing mechanism supports both checkpoint-free and checkpoint modes of log mining by the capture process. In addition, both the capture process and the apply process may employ an eager apply approach to increase processing capacity.

Combining capture and apply in a distributed information sharing system

Splitting and merging database object information sharing streams. Streams are also referred to herein as 'propagations'. Splitting and merging information sharing streams can be used to improve performance in a information sharing environment when a failed or slow DBS impacts the performance. In one embodiment, an auto split process monitors the progress of applying changes at each node and detects the presence of a failed or a slow node. Once the failed or slow node is identified, the auto split process splits the propagation such that the offending node is sent through a separate propagation. Furthermore, an auto merge process can be started to monitor the newly created separate propagation. At a later point, the new propagation can be merged back into the original stream. For example, if the offending node catches up with other nodes, the auto merge process merges the newly created propagation back to the original propagation.

Reconfiguring propagation streams in distributed information sharing

A checkpoint free log mining mechanism comprising a capture process and an apply process that are logically associated with each other may be provided in a database system. In an embodiment, log mining information published by the capture process to the apply process comprises a complete set of log information for each interesting transaction. A system change number of a start transaction record of a transaction may be used to represent a start time of the entire transaction. The capture and apply processes may work cooperatively to establish a safe time point in the form of a particular system change number in logs to begin mining, under various circumstances such as in an initial startup state, in a steady state, in a process restart scenario in the middle of checkpoint free log mining, or in a transition between the checkpoint mode and the checkpoint free mode.

Configuring an n-way multi-master information sharing topology. Adding a new node (e.g., database server) to the information sharing topology can be implemented as follows. Initially, the new node is added as a slave of a particular co-master in the information sharing topology. The objects to replicate are instantiated on the new node by propagating data from the particular co-master to the new node. Furthermore, a capture process is created on the particular co-master to send changes to the objects to the slave. Meanwhile, the co-masters continue to propagate changes to each other. To promote the slave to a master, changes to objects stored at the slave are propagated to each of the co-masters. Furthermore, changes at each of the masters are propagated to the promoted node.

Growing community of inventors

Foster City, CA, United States of America

Lei Gao