Data Manipulation Language Statements › #TREQ › Regular and Execute #TREQ Description

Regular and Execute #TREQ Description

The regular and execute versions of the #TREQ statement request a transfer of data from the issuing program to the physical terminal and/or from the physical terminal to the program. The requested transfer is designated as synchronous or asynchronous:

• Synchronous—Control is not returned to the issuing program until the I/O operation is completed. Synchronous transfer is accomplished by using #TREQ GET, PUT, PUTGET, or ALLOC statements.
• Asynchronous—Control is returned to the issuing program immediately after the requested I/O operation is initiated; the program continues to execute concurrently with the I/O operation. An event control block (ECB) is established that will be posted after the I/O operation is completed. Asynchronous transfer is accomplished by using the #TREQ READ, WRITE, WRITREAD, or ALLOC statements.

  An asynchronous request must be followed by a #TREQ CHECK before continuing with further terminal I/O operations to ensure that the previous #TREQ processing is completed. Most error message codes associated with #TREQ READ, WRITE, WRITREAD, or ALLOC requests are returned when the #TREQ CHECK statement is issued.

To send a data stream immediately to a terminal or group of terminals, you can issue a #TREQ WRITE/PUT (blast) request, using the DESTID, USERID, and LTERMID parameters. For write-direct-to-terminal requests, the system ignores the SAVE, EOT, and TRANSPAR options. Write-direct-to-terminal requests are not supported for list #TREQ requests.