A new buffer replacement scheme, called DEAR (detection-based adaptive replacement), is presented for effective caching of disk blocks in the operating system. The proposed DEAR scheme automatically detects block reference patterns of applications and applies different replacement policies to different applications depending on the detected reference pattern. The detection is made by a periodic process and is based on the relationship between block attribute values, such as backward distance and frequency gathered in a period, and the forward distance observed in the next period. This paper also describes an implementation and performance measurement of the DEAR scheme in FreeBSD. The results from performance measurements of several real applications show that, compared with the LRU scheme, the proposed scheme reduces the number of disk I/Os by up to 51 percent, and the response time by up to 35 percent in the case of single application executions. For multiple application executions, the results show that the proposed scheme reduces the number of disk I/Os by up to 20 percent and the overall response time by up to 18 percent.