In-memory database

Memory database. As the name implies, put the data in the memory of the direct operation of the database.

In contrast to disk, memory data reads and writes more than a few orders of magnitude, saving data in memory compared to on-disk access can greatly improve the performance of your application. At the same time. The memory database discards the traditional way of disk data management, and the architecture is designed again in memory based on all data, and the corresponding improvements are made in data cache, high speed algorithm and parallel operation. So data processing speed than the traditional database processing speed is much faster, generally more than 10 times times. The most important feature of the in-memory database is its "primary copy" or "Working version number" resident memory, which means that the active transaction only deals with the memory copy of the real-time memory database.

The similarities and differences between memory database and traditional database

The traditional database system is a relational database, and the purpose of developing such a database is to deal with permanent and stable data.

The relational database emphasizes maintaining the integrity and consistency of the data. However, it is very difficult to take into account the relevant data and its processing timing constraints, can not meet the needs of industrial production management real-time applications. Because the real-time transaction requires the system to forecast the transaction execution time more accurately.

In the case of disk databases, the actual average running time of transactions differs greatly from the estimated worst-case run time due to disk access, data transfer in and out of storage, buffer management, queued waits, and latency of locks. Assume that the entire database or its basic "work" section is put into memory so that each transaction does not have I/O during the run. The system calculates and schedules the running time of the transaction more accurately. So that it has a good dynamic predictability provides a strong support. At the same time, it lays the groundwork for implementing the timing constraints of the transaction. This is the main reason for the memory database to appear.

The data processed by the in-memory database is generally "short-lived", that is, it has a certain amount of time, and new data is generated when obsolete, and the current decision derivation becomes invalid.

Therefore, the actual application of memory database to handle the real-time business logic processing of strong data.

The traditional database is designed to deal with permanent and stable data, its performance target is high system throughput and low cost, processing the real-time data of the relatively little consideration. In practical application, the traditional database is used to store the data with low real-time requirement.

In practical applications, these two databases are often used in conjunction, rather than in a memory database instead of a traditional database.

Common memory databases

Sqlite

SQLite is a Open Source Memory Database , which realizes the Independent, embeddable. 0 configuration of the SQL database engine.

http://www.sqlite.com.cn/  

Oracle TimesTen Memory Database

Oracle TimesTen is a completely redesigned memory database.

It implements data storage using row-based relational models (tables, columns, data types, indexes, and so on). and use SQL as the language of the interview.

It provides a number of APIs and supports Oracle PL/SQL. Application access is identical to other relational databases.

http://download.csdn.net/detail/xunzaosiyecao/7307121l  

IBM SolidDB  

The IBM SolidDB provides throughput rates of tens of thousands of to hundreds of thousands of transactions per second, and is always able to obtain microsecond response time (or latency).

http://www-01.ibm.com/software/data/soliddb/  

Sap-hana

http://help.sap.com/hana/  

SQL Server Hekaton Memory Database engine

http://www.cnblogs.com/CareySon/p/3155753.html  

Other references:

http://www.searchdatabase.com.cn/guide/imdb.htm  
http://hemeicun.blog.163.com/blog/static/11157304820113645525209/  

In-memory database