70.You executed the following SQL statement to shrink the EMPLOYEES table
segment stored in the
EXAMPLE tablespace:
ALTER TABLE employees
SHRINK SPACE CASCADE;
Which statement is correct in this scenario?
A. The EMPLOYEES table will be changed to read-only mode during the shrink
operation.
B. The indexes created on the EMPLOYEES table will need to be
rebuilt after the shrink operation is over.
C. The shrink behavior will
be cascaded to all dependent segments of the table that support a shrink
operation.
D. Data manipulation language (DML) operations will not
be possible on the EMPLOYEES table during
the COMPACTION phase of the
shrink operation.
Answer: C
解析:
http://docs.oracle.com/cd/E11882_01/server.112/e25494/schema.htm#ADMIN10161
Segment shrink is an online, in-place operation. DML operations and queries can be issued during the data movement phase of segment shrink. Concurrent DML operations are blocked for a short time at the end of the shrink operation, when the space is deallocated. Indexes are maintained during the shrink operation and remain usable after the operation is complete. Segment shrink does not require extra disk space to be allocated.
Shrink operations can be performed only on segments in locally managed tablespaces with automatic segment space management (ASSM). Within an ASSM tablespace, all segment types are eligible for online segment shrink except these:
IOT mapping tables
Tables with rowid based materialized views
Tables with function-based indexes
SECUREFILE LOBs
Compressed tables
原文：http://www.cnblogs.com/bowshy/p/3677265.html