An index was created in support of the primary key constraint—that is normal—but what about the other two segments, the LOBINDEX and the LOBSEGMENT? Those were created in support of our LOB column. The LOBSEGMENT is where our actual data will be stored (well, it might be stored in the table T also, but we’ll cover that in more detail when we get to the ENABLE STORAGE IN ROW clause). The LOBINDEX is used to navigate our LOB, to find the pieces of it. When we create a LOB column, in general what is stored in the row is a pointer, or LOB locator. This LOB locator is what our application retrieves. When we ask for “bytes 1,000 through 2,000” of the LOB, the LOB locator is used against the LOBINDEX to find where those bytes are stored, and then the ...
Get Expert Oracle Database Architecture, Third Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
