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oracle - What happens when table size is bigger than data block size?

问题描述:

I understand that Oracle organizes data blocks into extents, and you should define initial and next extent when creating a table, so when table size becomes bigger than the size of the extent, a new extent is obtained.

But what happens when table size exceeds the size of the data block?

I'm assuming that the whole point of extent is to make sure the table size never exceeds the data block size, am I correct with my assumption?

Please explain in layman terms.

网友答案:

Block is the smallest logical allocation unit, far smaller than extent or segments, size varies between 2 and 32 kB, 8 kB is the default size. An extent consists of blocks, a segment consists of extents. A simple, heap, non-partitioned table without LOB based columns is logically represented by single segment.

Here is a brief overview:

https://docs.oracle.com/database/121/CNCPT/logical.htm

Btw. a table is always bigger than one block (if it has data) it has header and extent allocation blocks which in total is usually 3 blocks then table data is in following blocks.

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