Hi Yohai,
The XCOM for z/OS team wants you to know that OPENSSL has been supported by XCOM for z/OS and Windows for many years. Please note that encrypting data does require extra overhead and will impact performance as compared to running non-OPENSSL transfers. There are also many environmental factors, such as hardware, network, and CPU to name a few, that can affect performance and that are outside of XCOM’s realm. If performance is your concern, we suggest that you try running different test transfers at your site and have your network administrator use any available packet analyzer such as Wireshark to trace the connection between the two systems. This should help you in verifying the performance of transfers as well as seeing that XCOM is indeed encrypting the data being sent.
Regards,
The XCOM for z/OS Team