SharePlex for Oracle

Architecture

The original member of the SharePlex® family of replication products, SharePlex for Oracle allows you to meet your business continuity and performance needs by utilizing a technical architecture superior to any other replication product. SharePlex for Oracle provides asynchronous, fault tolerant, streaming and near real time replication of the Oracle database.

The key benefits of using this architecture

• Maintains a current, available database for multiple uses
  
• Fast and accurate, imposing virtually no overhead on the production instance
  
• Scalable and complete, able to replicate business volumes of data now and evolve with your growing needs
  
• Resilient to common outages
  
• Engineered by industry experts
  
• Able to facilitate 24x7 operation by helping eliminate planned downtime with the Reconcile option
• Easier to use with new automation and reporting features
  

Foundation Architecture

The following illustration will provide a basic conceptual understanding of how SharePlex works. There are many more details involved in replication.

Capture

The SharePlex capture process gathers changes with virtually no overhead on the production database. In capture process:

• The capture process reads from the Oracle redo logs, so the process of replication does not add performance loads to the production instance.
• The network transports only changes to replicated objects, (not the rest of the database housekeeping information contained in the redo logs) so the SharePlex network usage is very low and consistent.
• Database resources are not required to capture and move the data. A small repository does reside in Oracle to record information such as when replication started/stopped, etc.
• The capture process within SharePlex can read the online redo logs, go back through archive logs and even prompt for archive logs which have been taken off line to secondary storage. It is this capability that adds to the fault tolerance. For example, if the capture process is terminated for some reason, it can literally go back in time.

The capture process resides on the source system, reading the online redo logs automatically generated by Oracle. These reads of the redo log are completed as file system reads and not through the database. By using the redo logs as our source of change information, Quest is able to replicate the changes to the production database without incurring additional overhead on that instance. Oracle uses the redo logs for their database recoverability. As a result, the redo logs are a reliable source of change information, whose format is fairly stable. Quest has reverse engineered the format of the redo logs starting with the Oracle 6 release (that version is now retired but SharePlex supports replication of subsequent Oracle versions starting with the 7.3.4 release), and Shareplex is now able to handle the new format of oracle 9i and 10g redo logs.

The capture process monitors the redo logs for changes continually. When a record appears in the redo logs, SharePlex determines if it is for an object to be replicated. If it is, SharePlex adds addressing information such as to which hosts the change should be sent and then puts the change information into its queues. The queues reside outside the database. The data is immediately processed and transported to the target systems without waiting for a commit or a rollback, which would introduce unnecessary latency. (When a commit or rollback appears in the redo logs, it is subsequently sent, and the transaction is appropriately completed on the target systems.)

Transport

SharePlex uses its own network protocol combined with TCP/IP to transport data between the source and target systems. The process confirms the receipt and the appropriate order of the network packets, providing fault tolerance for network interruptions while ensuring data integrity and completeness. No additional middleware is required to transport the data.

Posting

The SharePlex post process converts the change information into SQL statements. The SQL statements are then applied to the open target instance using standard SQL*Plus connections. Because SharePlex updates the target instances using standard SQL like any other application, the concern about its supportability from Oracle is unwarranted.

Part of the key to SharePlex' accurate replication is its ability to maintain Oracle's read consistency from source to target, not only replicating the order of the transactions, but also their context. SharePlex replicates the combination of updating transactions to the target as they occurred on the source, so that the resulting replica is reliable for disaster recovery. To accomplish this, SharePlex creates connections to the target database to mirror the updating connections on the source system, so that transactions can be applied to the target instance in parallel, as they occurred on the source.

Using the Foundation

SharePlex supports a variety of configurations to meet your high availability or load balancing needs. SharePlex is not limited to replicating simply between source A and target B in one direction, although there is tremendous value in this architecture alone. Examples include:

Load Balancing/Reducing Query Contention

Use the up-to-the-minute, fully accessible database for ad hoc querying and reporting to reduce contention and improve performance on your production system. For more information, please see our white paper, "Creating an Accurate Reporting Instance to Achieve Load Balancing" (39.5 KB requires Adobe Acrobat)

Today’s enterprise requires constant availability for its data and processes. SharePlex can provide an alternate copy of production data for failover in case a server goes down or if maintenance is required.

Distributed Processing

The peer-to-peer configuration enables you to distribute users to different servers, keeping all copies of the database current with changes from each of the other servers. In this configuration, SharePlex applies conflict resolution as required by the circumstance and as defined by your business needs. For more information about creating a highly available database, see our white paper, "Building a 24x7 Database" (54.9 KB requires Adobe Acrobat). This scenario provides the fastest possible fail over time that can be achieved using any technology in a wide area network environment for disaster recovery.

Broadcast and Consolidated Replication

SharePlex replicates in real-time over both local area and wide area networks (LAN and WAN) to disseminate copies of production data wherever needed. For broadcast replication, remote users gain access to up-to-date data without logging on to the production server, improving network and OLTP performance.

Data Distribution Across the Globe

If you need to replicate data to a target that is not directly connected, SharePlex supports cascading replication. Using this configuration, for example, you can replicate data between long distances (e.g., from New York to Tokyo.) SharePlex can support numerous complex replication scenarios to meet your needs. In this cascading example, no Oracle software is required on this node if it will only be acting to store and forward.

Related Solutions

SharePlex FS is a powerful, flexible solution that replicates changes to initialization files, data files, log files, archived files, compressed files, FTP servers, applications, Web servers, mirror sites and more.

SharePlex FS provides the same SharePlex technology for variety of file systems. When understanding the architectures, which can be constructed using SharePlex, it is important to think of the basic replication from database A to database B as building blocks or the foundation architecture. Sophisticated solutions in the final architecture are ultimately created using the foundation architecture. Each of these solution architectures is presented.

Benefits of SharePlex® for Oracle

SharePlex® is fast, with just seconds of latency between the source and target. Adhering to the Oracle Read Consistency Model, it maintains both operation order and session context all the way to the target instance, where SharePlex uses standard SQL to apply the transaction. Log-based replication imposes virtually no overhead on the source database and source system. The reason for this is the way in which the data is extracted: reading the log files from the operating system. The network traffic is very light because TCP/IP without additional middleware is used to transport only the changes to the database and not all of the geometry information required to run recovery.

Scalable and Complete

Replicating thousands of tables with volumes of over a thousand transactions per second means that SharePlex handles business-volumes of data and can evolve with your throughput needs. Actual throughput rates are affected by the performance of the servers involved, size of the network pipe and transaction mix. Any logical replication of a database is effected by these issues. SharePlex supports replication of tables with long columns and referential integrity enabled, tables without a primary key, and sequences in the Oracle database. SharePlex provides replication of objects for packaged applications including:

• Banner
• Baan
• Geoquest
• PeopleSoft Enterprise One
• Oracle eBusiness Suite
• PeopleSoft
• Peregrine
• Remedy
• Retek
• SAP
• Siebel
• Vantiv
• And many more……

In addition, SharePlex replicates the ALTER TABLE and TRUNCATE commands, enabling it to replicate DDL activities not supported by other software replication tools.

Reconcile Option

Any high availability product should not reduce your availability. As such, SharePlex can be installed and the target established without an interruption to either the source database or machine:

• Simplifies the process and reduces the time it takes to initiate or re-establish replication by allowing you to make a copy of your database on-the-fly and start replicating quickly
  
• Works in conjunction with Oracle's Hot Backup, disk mirroring, and other physical refresh technologies to enable 24x7 operations and minimize system downtime
  

Database replication ensures 24x7 information availability. However, establishing replication can require extensive system downtime – until now. SharePlex allows you to use Oracle's Hot Backup, disk mirroring, and other advanced physical refresh technologies to create a copy of your database instance with almost no production system downtime. Data is accessible during the resync and users stay productive. Once you have a copy of the database, it can then be updated by SharePlex for Oracle and used for disaster recovery, high availability, process load balancing, reporting, and ad-hoc queries.

Resilient to Common Outages

SharePlex was designed with performance and resilience in mind. SharePlex can tolerate instance failures on either the source or target systems, and it does not require special recovery steps if such problems occur. SharePlex can tolerate redo logs being recycled, network failures, and even system failures. Its high-speed replication includes many features to minimize overhead and latency while providing security, including its use of TCP/IP for transporting transactions. The combination of TCP/IP and SharePlex proprietary network protocol guarantees that transactions will not be lost during network transport, even if the network service is interrupted. It is the use of queue files outside the database that ensure resiliency. Should any component of the replication architecture fail and be recoverable, SharePlex will pick up where it left and continue replicating without any transaction loss and in an automated fashion.

Engineered by Industry Visionaries

Industry leaders have created this product for superior replication. Eyal Aronoff, CTO at Quest Software and author of Oracle Development and Tuning, heads the development of SharePlex. For more information about SharePlex replication, see our white paper, "High Speed Replication for Oracle" (41.9KB requires Adobe Acrobat).