Second chance replacement policy for mobile database overflow

The visitor location register (VLR) is used to store temporary records for roaming users. Due to the limited capacity, the VLR may be full. This phenomenon is called VLR overflow. By replacing an existing record, the incoming user can still receive services. The most-idle replacement (MR) policy was proposed to improve the random replacement (RR) policy. The MR policy is almost the optimum method and outperforms RR policy significantly. However, the MR policy requires global information to find the most-idle user. It needs considerable extra cost and is unfeasible due to the separated VLR databases in the real mobile network. Therefore, we propose the second chance replacement (SCR) policy to overcome these drawbacks. The SCR policy needs only an additional bit in the record. Partial information is sufficient for our method, so it is feasible in the real mobile network. Moreover, the simulation results show that the SCR policy outperforms the MR policy in most scenarios investigated in our study.