SPLF, OUTQ, DTAQ, DTAARA

 Spooled File

Spooling is a system function that saves data in database file for later processing or printing. This data, which is saved and eventually printed, is called a spooled file (or printer output file). When spooling is used, spooled files are created from the application pgm, from a system pgm, or by pressing the Print Key. These files are put in places called output queues.
spooled file,假脱机文件, 用于存放后续要处理或打印的文件. 在output queue中存放.

Output Queue (OUTQ)

Output Queues are objects, defined to the system, that provide a place for spooled files to wait until they are printed. Output queues are created by a user or by the system.

本质是一个queue队列, 用于存放spooled file(假脱机文件).

Data Queue (DTAQ)

Data Queues are a type of system object that you can create, to which one HLL procedure or pgm can send data, and from which another HLL procedure or pgm can receive data.

The receiving pgm can be already waiting for the data, or can receive the data later.
用于多个程序(pgm)间的communication.  异步通讯最常用的手段.

Data Area (DTAARA)

A Data Area is an object used to hold data for access by any job running on the system.
可用于多个程序(pgm)间的communication.
也可以用于存放一个多pgm都可用的共用变量, 例如存放一个server name, 每个用到的pgm都可以访问, 并且修改的话只用修改一处, 方便维护.