216.Which three elements can a job chain process involve? (Choose three)A. an eventB. a scheduleC. a programD. another chain E. a lightweight jobAnswer: BDE答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/scheduse.htm#ADMIN12458Defining Chain Steps
创建chain对象之后，定义一个或多个chain步骤。每一步都可以指向下面的一个步骤:A Scheduler program object (program)--包含 lightweight job Another chain (a nested chain) An event schedule, inline event, or file watcher 下面的PL/SQL块创建一个轻量级作业。轻量级作业必须引用一个程序，程序类型必须是'PLSQL_BLOCK'或'STORED_PROCEDURE'。此外，在创建作业时，程序必须已经启用。BEGIN DBMS_SCHEDULER.CREATE_JOB ( job_name => 'my_lightweight_job1', program_name => 'polling_prog_n2', repeat_interval => 'FREQ=SECONDLY;INTERVAL=10', end_date => '30-APR-09 04.00.00 AM Australia/Sydney', job_style => 'LIGHTWEIGHT', comments => 'Job that polls device n2 every 10 seconds');END;/
