Planar diodes fabricated with nano-structured silver oxide thin film show resistive switching effects. These structures can be programmed by voltage into two distinct resistive states and they are promising candidates for resistive random access memory (RRAM) devices. Cycle endurance on/off ration and charge retention are high. This wok provides insight into the mechanisms leading to the memory effects and to charge transport in these memory structures. Temperature dependent measurements show that charge carrier transport has activation energy of 70 meV suggesting that tunneling is the operating mechanism in both resistive states. The change in resistance is caused by a large increase in charge carrier density. This finding is explained by assuming that carrier transport takes place through a percolative network of micro-conducting paths.