Can any one let me know …if there is any chance of data duplication by any webMethods notification …if there is a chance how can we identity it and how to avoid it


You can avoid duplicate publish but not data duplicates. If you are looking for data duplicates, you need to come up with custom logic. [Although this is very rare case, as tables have primary or references keys].

Ref: http://techcommunity.softwareag.com/ecosystem/documentation/webmethods/adapters_estandards/Adapters/JDBC/JDBC_6-5/6-5_JDBC_Adapter_Install_and_Users_Guide.pdf
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Adapter notifications can use the Exactly Once notification feature. This feature ensures that notification data will not be duplicated even if a failure occurs during processing. This is achieved by assigning unique IDs for each publishable document. After a processing failure, Integration Server checks for duplicate records in storage and ignores any duplicate IDs.