Direct And To The Point
By Sam Drake on Dec 09, 2011
In my previous post I explained how the TimesTen In-Memory Database is a very fast relational database. Like any relational database, TimesTen executes standard SQL via standard APIs Because of TimesTen’s “In-Memory” architecture, TimesTen can often use fewer CPU cycles than competing technologies to achieve the same result … yielding very fast response times.
In addition to its use of RAM, TimesTen provides another feature which helps it to provide very fast performance.
Relational databases, including TimesTen, let applications running on many machines access the database. Applications make use of a client library or driver which provides the database API. When the application calls that API – to execute SQL or fetch a row, for example – the client library formats the request from the application into messages, which it then transmits to the database server. Typically TCP/IP is used for communication.
On the database server, a process reads those messages from the network and processes them…accessing or modifying data in the database. Any results from the operation are then, in turn, packaged up into messages and sent back to the client from the database server.
This “client/server” design makes a lot of sense, and nearly all databases – including TimesTen – support it. However, TimesTen supports another alternative as well.
TimesTen actually provides two different sets of libraries/drivers that applications can use. Both sets provide the same APIs – JDBC, ODBC, OCI, Pro*C. One set, the “client/server drivers”, work as explained above. The others, called “direct mode” drivers, work in a more streamlined manner.
The TimesTen database engine is included in its direct-mode drivers. When an application calls a direct mode driver to execute SQL or fetch rows the driver doesn’t package that request into messages. Instead, the driver in turn directly calls the TimesTen database engine, which executes the request directly. This is done without the overhead of packaging requests and responses into messages, and without the overhead of transmitting those messages on a network. In fact, since the database engine runs in the customer’s application process, there isn’t even any context switch or IPC (inter-process communication) overhead!
By using direct mode drivers instead of client/server drivers, applications can achieve dramatic performance results. SQL can easily be executed in microseconds (millionths of a second) instead of the typical milliseconds or more. When combined with the fast performance provided by TimesTen’s in-memory architecture, direct mode applications can achieve levels of performance that are hard to beat.
Since both direct mode and client/server mode drivers provide the same APIs and capabilities, applications don’t need to be modified to use direct mode. Both modes can be used simultaneously, so some very response time critical applications might use direct mode while other, less critical applications use client/server.
When applications run on the same machine that contains the TimesTen database, they can use either TimesTen’s client/server or direct mode drivers. If the application runs on a different machine than TimesTen then the client/server drivers must be used.
Even in client/server mode, TimesTen provides very fast performance. But by eliminating the overhead of network round-trips and context switches entirely, direct mode can provide applications with the fastest possible access to data, while still using standard SQL, PL/SQL, and APIs.
Using direct or client/server database connections from JDBC: http://docs.oracle.com/cd/E13085_01/doc/timesten.1121/e13068/writing_app.htm#BABJIJHI
Using direct or client/server database connections from “C” applications: http://docs.oracle.com/cd/E13085_01/doc/timesten.1121/e13066/writing_app.htm#CEGGJGDG