Trabajo con Latches
What Are Latches? Latches are serialization mechanisms that protect areas of Oracle’s shared memory (the SGA). In simple terms, latches prevent two processes from simultaneously updating — and possibly corrupting — the same area of the SGA. Oracle sessions need to update or read from the SGA for almost all database operations. For instance: • When a session reads a block from disk, it must modify a free block in the buffer cache and adjust the buffer cache LRU chain1. • When a session reads a block from the SGA, it will modify the LRU chain. • When a new SQL statement is parsed, it will be added to the library cache within the SGA. • As modifications are made to blocks, entries are placed in the redo buffer. • The database writer periodically writes buffers from the cache to disk (and must update their status from “dirty” to “clean”). • The redo log writer writes entries from the redo buffer to the redo logs. Latches prevent any of these operations from colliding and possibly corruptin...