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SAP JCo is a communication library, based on RFC which is an SAP interface protocol that simplifies the programming of communication processes between systems. The RFCs enable you to call and execute predefined functions in a remote system, or in the same system.
The RFCs manage the communication process, parameter transfer and error handling. The SAP Java Connector needs the metadata of all Remote Function Modules (RFMs) that are to be used by a Java client. The metadata of the RFMs is retrieved dynamically from the ABAP server at runtime.

NOTE: For the configuration of RFC, JCo desintaions, JRA and JCo RFC Providers  the application manual needs to be checked. Application specific issues including JCo configuration topics need to be addressed by the respective application component (in such cases BC-MID-CON-JCO team is not responsible). SAP JCo is only a development library and framework which offers the SAP RFC protocol to the Java world. So there is no business or processing logic associated with it. It is a messenger for data transmissions only.

  • Activation JCo tracing at startup using JVM parameters:
    where trace level 0 means tracing off
  • Activation JCo tracing via API calls:
    JCo.setTrace(<level>, <path>) or
  • File naming:
 Trace Levels in JCo 3
Trace Level

AS Java severity level

JCo 3 Trace content
 0 NONEno  trace 
ERROR  JCo version and runtime environment info
+ JCo internal errors and exceptions without application errors
 2 WARNING+ JCo warning messages (e.g. non-ABAP system exceptions)
 3 INFO+ JCo information messages (e.g. ABAP exceptions)
PATH + RFC calls and important public API calls
 DEBUG+ important internal middleware calls
+ codepage information
 6 DEBUG+ connection attributes
+ ASCII content data (first 1000 chars of structures / first 5 rows of tables)
 7 DEBUG+ RFC metadata (name, type, offset, length, import/export options)
+ additionaly Hex values for content data 

+ full content data dump (no character or row llimits)

+ caller stack trace information (e.g. for getClient() - identifies application) 

DEBUG no additional information (reserved for future use) 
10 DEBUG no additional information (reserved for future use) 

 In NWA log configurator the tracing locations / are written into the global AS Java logging: defaultTrace.<#>.trc


JRFC trace
  • Global activation the JRFC trace using JVM parameter:
    0 - off, 1 - on
  • Global activation the JRFC trace via API call: JCo.setProperty("jrfc.trace", 1)
  • File naming:
  • Remarks:
    RFC trace flags are also propagated to AS ABAP systems for creating RFC tracese, files dev_rfc<WP#>
    RFC traces can be switched on for a JCo server instance from the AS ABAP system.
    The RFC trace settings of an SM59 destination is exported to a JCo server on its first call. It can only switched off again by restarting the JCo server instance.
    See Note 1890353 for further details.
    Note, after the JRFC tracing is activated the number and size of JRFC trace files can grow significally depending on the number ofr transactions.
RFC Error Logs

RFC error logs are written into dev_jco_rfc.<date>.trc / dev_jrfc.<date>.trc files, this logging cannot be switched off

 CPIC trace
  • Global activation using JVM parameter:
  • Global activation using API call:
    JCo.setProperty("cpic.trace", <level>)
  • Activationg for one specific connection using additional logon property jco.client.cpic_trace=<level>
  • File naming:
  • Remarks:
    CPIC trace flags are also propagated to the SAP gateway for creating CPIC traces there, dev_rd file. (gw/accept_remote_trace_level)
    CPIC traces can alos be switched on for a JCo server instance from the SAP gateway side (gw/export_trace_level, gw/export_trace_level_strict)
IDoc tracing:

Activating using JVM parameter: 



1077727 - SAP JCo 3.0 release and support strategy

549268  - SAP JCo 2.x release and support strategy

628962  - How to switch on the SAP JCo trace 

47682 - Activating the CPIC trace

532918  - RFC trace generation scenarios 

877979 - RFC tracing for external-to-ABAP communication

1507034 - Max number of gateway connections / Maximum number of conversations exceeded

52959 - sapms..., sapdp.., sapgw.. unknown (or not found)

568271 - Lifetime of an RFC connection

1135947 - Bean not found

1890353 - GW: gw/export_trace_level has no apparent effect

1166904 - Assertion ticket SSO for Web Dynpro Java JCO destinations

1791529 - GW: Hanging connections between J2EE and gateway

1069911 - GW: Changes to the ACL list of the gateway (reginfo)

896973 -  Service 'xyz' unknown; error in getservbyname/getaddrinfo


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