OCP 1Z0 052 140

funchile

140. Identify two situations in which the block header grows in a data block. (Choose two.)
A.when row directories need more row entries
B.when there is row migration in the data block
C.when there is an increase in the PCTFREE value for the data block
D.when more transaction slots are required than are initially configured
Answer: AD

http://docs.oracle.com/cd/E11882_01/server.112/e40540/logical.htm#CNCPT1051
Oracle Database stores rows as variable-length records. A row is contained in one or more rowpieces. Each row piece has a rowheader and columndata.


　　

　　

　　
Block header
This part contains general information about the block, including disk address and segment type. For blocks that are transaction-managed, the blockheader contains active and historical transaction information.
A transaction entry is required for every transaction that updates the block. Oracle Database initially reserves space in the block header for transaction entries. In data blocks allocated to segments thatsupport transactional changes, free space can also hold transaction entries when the header space is depleted. The space required for transaction entries is operating system dependent. However, transaction entries in most operating systems require approximately23 bytes.

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