You control an IK solution by setting joint precedence to determine which joints contribute the most to the IK solution and which joints contribute the least.
Joints with high precedence values are calculated first, and, therefore, contribute more motion to the IK solution. Joints with low precedence values are calculated last, and, therefore, contribute the least motion to the IK solution.
Joints with equal precedence values are calculated by their order in the hierarchy. Joints deeper in the hierarchy (closer to the end effector) are calculated first and joints closer to the root are calculated last.