A CLO compliance test that requires the ratio of the collateral pool's par value to the par value of each rated tranche to exceed a minimum threshold (e.g., Class A: OC_A = Collateral Par/Class A Par ≥ 120%). When the test fails — typically because defaults reduce collateral par — all cash flow that would have gone to equity and subordinate tranches is diverted to pay down the senior-most tranche until the OC ratio is restored. The primary mechanism by which loan-pool defaults translate into CLO-equity cash-flow impairment.