![]() The blocks being read may or may not be physically contiguous on disk. ![]() Since Oracle reads the blocks one at a time, it's called a "sequential read." However, the term "sequential" here refers to the order in which the blocks are read, not their physical location on the disk. The system call reads the block directly into the specified buffer in the buffer cache. In this case, Oracle issues a system call like pread on Linux, specifying the file descriptor, the block's offset on the disk, and the buffer to read the block into. It typically happens during indexed reads, such as when accessing data via an index or reading index blocks themselves.
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