Define a logical file using DDS

A logical file determines how data records are selected and defined when read by an application program. A logical file can be a simple, multiple format, or join logical file.

A simple logical file contains one record format and has one file specified on the PFILE keyword. A multiple format logical file either contains more than one record format or has more than one file specified on the PFILE keyword. A join logical file contains one record format and has up to 256 files specified on the JFILE keyword.

• Simple and multiple format logical files in DDS
  You must specify the PFILE keyword at the record level for simple and multiple format logical files. In a multiple format logical file, a record format can use only the fields common to all the physical files specified on the PFILE keyword for that record format.
• Join logical files in DDS
  Join logical files combine different fields from more than one physical file into a single record. You must specify the JFILE keyword at the record level for join logical files.
• Specify record formats in a logical file in DDS
  If there is more than one record format specified in a logical file, you must specify the PFILE keyword for each record format.