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OAPI Technical Documentations

Overview of DCASS OMnet Application Programme Interface (OAPI)

Clearing Participants can connect to DCASS via HKEX’s Central Gateway in two ways: (i) using the browser based frontend application, namely DCASS Online; and/or (ii) using customized OMnet Application Programme Interface (OAPI). DCASS Online is designed to support CPs with low to medium clearing volume as it facilitates manual input of post trade instructions.

Through DCASS OAPI, Clearing Participants can connect their back-office system to DCASS to enable straight-through-processing which can support high clearing volume. As information from DCASS will be updated on real time basis, the direct host-to-host connection alternative provided by OAPI can help Clearing Participants to improve their operational efficiency and provide better risk management control.

Development of DCASS OAPI

Clearing Participants can develop DCASS OAPI themselves or acquire from software developer. Clearing Participants can approach HKEX to obtain the OAPI documentation for developing their DCASS OAPI. Due to the licensing obligations between HKEX and the software vendor, the DCASS OAPI Manual is password protected. Clearing Participants who wish to download and open DCASS OAPI Manual, please contact DCASS Hotline at (852) 2979 7222 or email to to obtain the password. 

DCASS OAPI testing environment is available for Clearing Participants to test their DCASS OAPI and access to testing environment is subject to charge.

Certification Arrangement

Prior to the production rollout of DCASS OAPI, Clearing Participants are required to arrange with HKEX to conduct certification test. Only certified DCASS OAPI is allowed to put into production and any modification is subject to re-certification by HKEX.


Particulars Amount
  • Access to DCASS OAPI testing environment
100/business day or part thereof provided that no access fee will be charged for the first 5 business days
  • DCASS OAPI connection via Central Gateway
  • DCASS OAPI certification
2,000/test regardless of test results

Updated 20 Apr 2020