After a worker is created, you can't update or delete the user information or roles though the worker service. Make updates though the User service

HDL Error: After a worker is created, you can't update or delete the user information or roles though                       the worker service. Make updates though the User service

If you have already loaded the worker you can not use Worker.dat file to load User Information. Worker.dat file can only be used at the time of new worker creation, if the worker already exists in the system then you need to use User.dat file to add/remove roles or to update the user account information.

In the User.dat file, discriminator User accepts only one role per user at a time. If you want to add multiple roles for a user at the same time, please use UserRole discriminator.

HDL Error ORA-01000: maximum open cursors exceeded

While uploading large volume of data in Cloud/EBS you may encounter this error message. The solution is to increase the value set for open_cursors for the session.

It was easy to amend this value in EBS
ALTER system SET open_cursors = 1000 scope=both;

But in Cloud you do not have access to do so but you can try optimizing the HDL performance.
Increase the size of below parameters in the HCM Data Loader configurator.

Maximum Concurrent Threads for Load
Load Group Size

The recommended value for the number of threads is 8, and for say 50,000 records in a batch, a Chunk size of 500 could be used to give decent throughput.

Navigation> Setup and Maintenance > Configure HCM Data Loader

If it doesn't improve the performance please raise a service request with Oracle and they will increase the value for open_cursors parameter.

Ref: (Doc ID 2066732.1)