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How do I resolve the error "JCO_ERROR_CONCURRENT_CALL" when running SAP JCo in a Web application?

Here is the exception report:$Exception: (132) JCO_ERROR_CONCURRENT_CALL: Concurrent call. Connection currently used in another thread.
at$Client.execute(Unknown Source)
at$Client.execute(Unknown Source)
at$Repository.execute(Unknown Source)
at$Repository.queryFunctionInterface(Unknown Source)
at$Repository.queryFunctionInterface(Unknown Source)
at$Repository.getFunctionInterface(Unknown Source)
at$BasicRepository.getFunctionTemplate(Unknown Source)

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From the looks of the exception, you have inadvertently created a singleton instance of the JCo connection somewhere and are trying to use the same connection at the same time. The best way to resolve this is to use JCo's built-in connection pooling. A JCo connection pool can be setup when the server launches and provide connections to any number of clients connected to the server (depending on the number of connections you make available in the pool). Do a search for "jco connection pool" on for tips on how to implement a connection pool in SAP JCo.

This was first published in July 2006

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