ORACLE Data Buffer DB cache

ORACLE Data Buffer DB cache db cache is a buffer organized by data blocks. When the database was just started, there was almost no user data buffer in the db cache, when a session accesses a table or index in the database, it first checks whether the data exists in the db cache. If the data does not exist, it reads the data block from the data file to the db cache, then read the data from the database CACHE. The data block in the database CACHE is located through the hash algorithm. There is a hash chain structure where all the data blocks being used in the buffer are located. If you want to search for data blocks, hash the chunk of the chunk chain. Scan the two-way linked list structure of the chunk to find the chunk. Each chain is called a BUCKET. The number of buckets does not change after the database is started. The number of buckets is specified by the parameter _ DB_BLOCK_HASH_BUCKETS. Db cache is composed of BUFFER. There are two algorithms in db chache. The LRU algorithm is used to swap out the buffer, and there is also a hash.