Oracle read-Write separation architecture

The separation of Read and write is an important idea of architecture distributed system. A lot of system overall processing capacity and can not keep pace with the growth of the business, so will inevitably bring bottlenecks, simple upgrade hardware can not be once and for all. For the characteristics of the business type, we need to make a series of adjustment from the architecture mode, such as dividing the business module, splitting the database and so on.

Centralized and distributed are two opposing models, the application characteristics of the industry also determines the structure of the idea. For example, some portals in the Internet industry, for technical and cost reasons, more open source database products (such as MySQL), because most of the typical read and write less requests, so for MySQL and its replication technology to provide the conditions. In contrast to some traditional intensive trading industries, such as telecommunications, finance, etc., taking into account the single-point processing capacity and reliability, stability and other issues, may more use of commercial databases, such as DB2, Oracle and so on.

On the database level, most of the traditional industry core library uses a centralized architecture idea, the use of high-provisioned minicomputer as host carrier, because the database itself and the host powerful processing capacity, the database can generally support the operation of the business, therefore, the Oracle read-write separation of the architecture relative to MySQL, relatively less.

A period of time has been planning the company's new database architecture, taking into account our business characteristics, the use of Oracle Read and write separation of ideas, writer DB and Reader db using log replication software for real-time synchronization; writer DB is responsible for real-time transaction-related query and transaction processing, Reader DB is responsible for read-only access, processing some non-real-time transaction details, report class summary query and so on. At the same time, in order to meet the requirements of high availability and scalability, the read-write end of the appropriate extension, such as writer db with HA or RAC architecture mode, Reader DB can be multi-set, through load balancing or business separation in the way, effectively share the pressure of reading library.

For the Shared-nothing database schema mode, one of the core problems is the real-time synchronization of the read-write library, and while reader DB is only responsible for business queries, it does not mean that the database is functionally read-only. Read-only is from an application perspective, in order to ensure data consistency and conflict considerations, because the query business module may need to involve some intermediate processing, if you need to process in the database (depending on the application requirements and design), so reader db still needs to be writable.

Let's talk about the problem of data synchronization technology selection:

There are many techniques for real-time data synchronization, based on the OS layer (for example, Veritas VVR), Storage-based replication (which is mostly supported in high-end storage), application-based distribution, or database-layer based technology. Because data synchronization may not be a single DB full-Library synchronization, it involves issues such as business data selection and multi-source consolidation, so OS replication and storage replication are often not the preferred technology for read-write separations.

Log-based Oracle replication technology, Oracle's own components can be implemented, but also has mature commercial software. Choosing a commercial standalone product or Oracle's own component capabilities depends on a variety of factors. such as the team's corresponding technical operation and maintenance capacity, project input costs, business system load level.

With Oracle's own component capabilities, no logical Standby, stream, and 11g physical Standby (Active Data Guard), the stream is the most flexible, but most unstable, 11g physical Standby supports recovery and read-only parallelism, but because it is not a logical application mechanism of logs, it is most limited in the scenario of read-write separation. Using Oracle's own components is entirely feasible if the technical team is sufficiently informed about the technology and the processing power of the selection scheme can support data synchronization requirements.

Choose commercially available products, more for stability, processing power and more. There are a number of mature Oracle replication software on the market, whether it is a veteran shareplex, or the realsync of the local DSG company and the Nine Bridge Company DDS, or Oracle upstart Goldengate, is a choice of objectives. With the acquisition and promotion of Goldengate by Oracle, individuals believe that goldengate will be a big hit in disaster tolerance, data distribution and synchronization.

Of course, the architecture good one reliable distributed read-write separation system, but also need to do a lot of application design, not in the scope of this article.

Oracle read-Write separation architecture