Hi, SymmetricDS is an asynchronous data replication software package that supports multiple subscribers and bi-directional synchronization. It uses web and database technologies to replicate tables between relational databases, in near real time if desired. The software was designed to scale for a large number of databases, work across low-bandwidth connections, and withstand periods of network outage. The software can be installed as a standalone process, as a web application in a Java application server, or it can be embedded into another Java application.
A single installation of SymmetricDS attached to a target database is called a node. A node is initialized by a properties file and is configured by inserting configuration data into a series of database tables. It then creates database triggers on the application tables to be synchronized so that database events are captured for delivery to other SymmetricDS nodes SymmetricDS supports synchronization across different database platforms through the concept of Database Dialects. A Database Dialect is an abstraction layer that SymmetricDS uses to insulate the main synchronization logic from database-specific implementation details. SymmetricDS is extendable through extension points. Extension points are custom, reusable Java code that are configured via XML. It captures the column values and record them in a table named sym_data. The triggers participate in the same transaction as the data change, and they record a unique transaction ID in sym_data also. Changes are batched together, given a batch ID, and sent to the target system. They are played back exactly as they occurred, in the same order. The batch is committed together for efficiency. All changes for the same transaction ID are guaranteed to be committed together. SymmetricDS has features found in both replication and synchronization products. It can be configured to create replicas with complete data sets, it is aware of transactions, and it replays data changes without merges. But instead of synchronously locking transactions, it allows all data changes to happen, then it periodically synchronizes the data to other databases. It's strengths are being able to sync a large number of databases (1000's) and allowing for clients to be temporarily disconnected. It's weaknesses are a higher latency (than transaction log parsers) and less mature conflict resolution. Here are some features: * triggers guarantee change data capture without special drivers for clients * driven by configuration, with advanced features supported through a Java API * horizontal and vertical data filtering and sub-setting and transformation * synchronization is scheduled at intervals or event driven * deployment can be to an application server, stand alone, or embedded in an application * clients can be disconnect for periods of time * web-based protocol that is compact and efficient and works with firewalls * data changes replayed exactly with no staging or merging of operations * database and operating system agnostic Root and node properties can be tweaked to control how data flows. SymmetricDS supports the concept of channels of data. Data synchronization is defined at the table (or table subset) level, and each managed table can be assigned to a channel that helps control the flow of data. A channel is a category of data that can be enabled, prioritized and synchronized independently of other channels. For example, in a retail environment, users may be waiting for inventory documents to update while a promotional sale event updates a large number of items. If processed in order, the item updates would delay the inventory updates even though the data is unrelated. By assigning changes to the item tables to an item channel and inventory tables' changes to an inventory channel, the changes are processed independently so inventory can get through despite the large amount of item data. It supports Firebird 2.0 and above. A UDF is needed by the database triggers. SymmetricDS includes the required UDF library, called SYM_UDF, in both source form (as a C program) and as pre-compiled libraries for both Windows and Linux. Deployment Options ------------------------------ Web application archive (WAR) deployed to an application server This option means packaging a WAR file and deploying to your favorite web server, like Apache Tomcat. It's a little more work, but you can configure the web server to do whatever you need. SymmetricDS can also be embedded in an existing web application, if desired. Standalone service that embeds Jetty web server This option means running the sym command line, which launches the built-in Jetty web server. This is a simple option because it is already provided, but you lose the flexibility to configure the web server any further. Embedded as a Java library in an application This option means you must write a wrapper Java program that runs SymmetricDS. You would probably use Jetty web server, which is also embeddable. You could bring up an embedded database like Derby or H2. You could configure the web server, database, or SymmetricDS to do whatever you needed, but it's also the most work of the three options discussed thus far. Grails Application A Grails SymmetricDS plugin is provided at the default Grails plugin site. This option ends up being a WAR deployment, but allows for the use of the Grails SDK for configuring and building the deployment. The plugin also provides Gorm (Hibernate) access to many of the core database tables. The only trouble I faced is the sym_udf entry point could not be found problem. This was solved by instsalling MS VC++ 2008 redistributable. The SymmetricDS forum is also very responsive. There are also some samples with the distribution. Regards. Sudheer Palaparmbil On Mon, Oct 10, 2011 at 11:00 PM, raja_s_patil <kpr.rspa...@gmail.com>wrote: > ** > > > > > --- In firebird-support@yahoogroups.com, Thomas Steinmaurer <ts@...> > wrote: > > > > >> Pls have a look at the open source project > > >> http://symmetricds.codehaus.org/ for synchronization. I have been > using this > > >> for the last 2 years > > >> with Firebird database. This works fantastically. You can sync both > ways, HO > > >> to branch as well as branch to HO. > > >> > > > > > > Yet another option for me. I visited the link you mentioned and I am > impressed with general Description. The idea of two tier replication is > simply fantastic. Since you are using it for last two years can you give us > general idea about it ? like how configuration is done, how is response time > (since its in Java), Can it function with Delphi application ? etc. etc. > Please also mention any problems you faced may be initially and resolved > later. > > > > I'm not using it, but interesting products. Check out Firebird-specific > information here: > > > http://symmetricds.codehaus.org/guide/2.4/html-single/user-guide.html#ap02-firebird > > > > > > A mandatory UDF library and limiting BLOB columns to 16K might be > > show-stoppers. > > > > > > Thanks Thomas Steinmaurer for making me aware of probable pitfall. > regarding using this product, I was addressing Mr. Sudheer, It was not > referring you. Anyways I will keep this option open as you have suggested, I > will discuss with client and arrive at final decision. After all he is going > to pay for licenses So his opinion is vital in going for a particular > product. We will be just evaluating technical aspect of all probable > solution and put forward a technical comparison as well cost benefit > analysis, ultimately he has to decide who will own his Money. If he decides > to drop the project all together, all our efforts are going to go to drain. > What to do, its part of life, cant help, but we can at most put all our > efforts in anticipation to to be successful. > > Thanks and warm regards > > R. S. Patil > > > [Non-text portions of this message have been removed] ------------------------------------ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Visit http://www.firebirdsql.org and click the Resources item on the main (top) menu. Try Knowledgebase and FAQ links ! Also search the knowledgebases at http://www.ibphoenix.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Yahoo! 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