In this paper, an OICA (Online Iterative Control Algorithm) by setting measured PES (Position Error Signal) into the servo system to achieve high track densities through minimizing the square of the H₂-norm of the transfer function from NRRO (Non-Repeatable Run-Out) disturbance sources to true PES is proposed without having to solve any AREs (Algebraic Riccati Equations) and LMIs (Linear Matrix Inequalities). An online RRO (Repeatable Run-Out) estimator is constructed to extract NRRO components for gradient estimates, hence preventing the controller parameters from being trapped in a local minima. Experimental results on a PC-based servo system for a spinstand [12] show an improvement of 22% in 3σ NRRO and suppression of baseline NRRO spectrum.