Investigate IXCJOIN's return and reason codes in the z/OS MVS Programming: Sysplex Services Reference.

With the introduction of z/OS® V1R10, IXCJOIN error IXCJoinRsnIsFailed, return code 8 and reason code 10x, could become more prevalent when a V1R10 or higher system is backed off to a lower level z/OS system. APAR number OA23153 has been created to prevent this situation from happening and should be installed to allow RRS to start on the lower level system. If the APAR is not available or installed, RRS must be removed from XCF before RRS can be started. For more details, see the "RRS use of XCF" section in z/OS MVS Programming: Resource Recovery at the V1R10 level or higher.