这个特性的引入伴随着几个新的隐含初始化参数：
SYS@ orcl> @GetHidPar
Enter value for par: undo_autotune
NAME VALUE PDESC
------------------------------ --------------- --------------------------------------------------
_undo_autotune TRUE enable auto tuning of undo_retention
SYS@ orcl> @GetHidPar
Enter value for par: collect_undo_stats
NAME VALUE PDESC
------------------------------ --------------- --------------------------------------------------
_collect_undo_stats TRUE Collect Statistics v$undostat
alter tablespace undotbs1 retention guarantee|noguarantee;
SYS@ orcl> select tablespace_name, contents, retention from dba_tablespaces;
TABLESPACE_NAME CONTENTS RETENTION
------------------------------ --------- -----------
SYSTEM PERMANENT NOT APPLY
SYSAUX PERMANENT NOT APPLY
UNDOTBS1 UNDO NOGUARANTEE
TEMP TEMPORARY NOT APPLY
USERS PERMANENT NOT APPLY
在数据文件autoextend off时，设置guarantee时当空间不足时会出现ORA-30036错误，在noguarantee时不会出现错误，这就是GUARANTEE与NOGUARANTEE的不同。