If I recently upgraded my Oracle client, why am I encountering this error?

An upgrade can sometimes leave behind remnants of the old client or fail to properly update the environment variables. The new client might have a different version of 'libclntsh.so' (e.g., 11.1 or 12.1). Ensure the `LD_LIBRARY_PATH` is updated to point to the new client's library directory. Also, check if any scripts or configuration files are still referencing the old library path.