|Oracle® Database Advanced Queuing User's Guide
12c Release 1 (12.1)
|PDF · Mobi · ePub|
This preface contains:
The following are changes in Oracle Database Advanced Queuing User's Guide for Oracle Database 12c Release 1 (12.1).
The following features are new in this release:
In Oracle Database 12c Release 1 (12.1), Advanced Queuing introduces high performing and scalable sharded JMS Queues. A sharded queue is a single logical queue that is divided into multiple, independent, physical queues through system-maintained partitioning. A sharded queue increases enqueue-dequeue throughput, especially across Oracle RAC instances, because ordering between two messages on different queue shards is best effort. Each shard is ordered based on enqueue time within a session. Sharded queues automatically manage table partitions so that enqueuers and dequeuers do not contend among themselves. In addition, sharded queues use an in-memory message cache to optimize performance and reduce the disk and CPU overhead of AQ-JMS enqueues and dequeues. Sharded queues are the preferred JMS queues for queues used across Oracle RAC instances, for queues with high enqueue or dequeue rates, or for queues with many subscribers.
See "JMS Sharded Queues" for more information.
Result Cache Enhancement
In Oracle Database 12c Release 1 (12.1), the Rules Engine introduces a result cache to improve the performance of many commonly used rules. The result cache will bypass the evaluation phase if an expression with the same attributes has already been evaluated earlier. Not all rule results are cached, such as when rule results are potentially non-deterministic or when not all rules are evaluated or when attributes include non-scalar data types. For Advanced Queues, the cache is most useful when subscriptions and their dequeue sessions are long-lived.
LONG VARCHAR Support
3-Tier Background Architecture
See "AQ Background Architecture" for more information.
Support for Data Guard Database Rolling Upgrade
Databases that use Oracle Database Advanced Queuing can now be upgraded to new Oracle database releases and patch sets in rolling fashion using Data Guard database rolling upgrades (transient logical standby database only). Rolling upgrades are supported beginning in Oracle Database 12c Release 1 (12.1).
Data Guard database rolling upgrades reduce planned downtime by enabling the upgrade to new database releases or patch sets in rolling fashion. Total database downtime for such an upgrade is limited to the small amount of time required to execute a Data Guard switchover.
The following packages will have support for rolling upgrade using logical standby:
DBMS_AQADM, except for the following procedures:
Oracle Database High Availability Overview for more information on Data Guard transient logical rolling upgrades
Oracle Database PL/SQL Packages and Types Reference for more information on the Oracle Database AQ packages