Week 02 Lecture (50)

File Manager (cont)

Access to a block of data proceeds as follows:

offset = BlockNumber * BLCKSZ
fileID = RelFileNode+ForkNumber
if (fileID is already in Vfd pool) {
    if (offset is in this file)
    	fd = use Vfd from pool
    else
        fd = allocate new Vfd for next part of file
} else {
    fd = allocate new Vfd for this file
}
seek to offset in fd
read/write data page (BLCKSZ bytes)

BLCKSZ is a global configurable constant (default: 8192).