Saturday, 10 August 2013

The JCL XMIT Statement: A Step-by-Step Guide.

XMIT JCL, How to use JCL XMIT statement
JCL XMIT Statement


Introduction.

The JCL XMIT statement is a powerful feature in Job Control Language (JCL) that plays a vital role in facilitating seamless data transmission between different JES (Job Entry Subsystem) or non-JES nodes. As a programmer, you must understand the syntax, and usage of the XMIT statement. 

In this article, we will explore how to use the JCL XMIT statement, provide examples illustrating its application, and delve into its syntax to ensure accurate implementation. Additionally, we will address the top five questions related to the JCL XMIT statement, providing valuable insights into this fundamental component of JCL data transmission.


Improving Data Transmission Efficiency with the XMIT Statement.

The XMIT statement is a powerful tool in JES2 that allows users to send jobs or data streams to other JES or non-JES nodes. Unlike other statements, the XMIT statement does not execute the job itself; instead, it facilitates the transmission of data to another node. 

Understanding the XMIT Statement.

The primary purpose of the XMIT statement is to transmit records from a JES2 node to either another JES2 node or an eligible non-JES2 node. For instance, it can be used to send data to VM or JES3 nodes. Notably, JES2 does not process or validate the records for JES2-specific requirements; it focuses solely on transmitting the data.

Building Header and Trailer Records.

Before transmitting the records, JES2 constructs header and trailer records based on the information provided in the JOB statement immediately preceding the /*XMIT statement. These records serve as markers and assist in data transmission. Once the header and trailer records are generated, JES2 transmits all the records that follow the /*XMIT statement.

Records and Transmission Types.

The records sent through the XMIT statement can be either a job input stream or an in-stream DD * or DD data set. If the records exist within a job input stream and the destination node has the capability to process Job Control Language (JCL), the transmitted input stream will be executed under the following conditions:

The record immediately following the /*XMIT statement must be a valid JOB statement at the destination node.

The input stream should solely consist of the JCL and associated data for the job referenced by the JOB statement.

However, it is crucial to note that if an NJE (network job entry) receiver detects multiple JOB statements within the input stream, all jobs will be flushed.

Determining the End of Records.

Several conditions dictate the end of records when utilizing the XMIT statement:
  1. The presence of the /* delimiter in the input stream.
  2. The identification of a two-character delimiter is specified using the DLM parameter on the /*XMIT statement.
  3. Exhaustion of card images within the input stream.
  4. Closure of the internal reader if records are being read from it.
  5. Syntax and Parameters

The /*XMIT statement follows a specific syntax and may include optional parameters. Here is an example illustrating the syntax:

/*XMIT {Nnnnn} [DLM=xx]
        {nodename}
        {nodename.userid}
        {nodename:userid}
        {nodename/userid}
        {nodename(userid)}
        {nodename.vmguestid}
        {nodename:vmguestid}
        {nodename/vmguestid}
        {nodename(vmguestid)}
        {name}

The /XMIT statement begins with the characters / in columns 1 and 2, followed by XMIT in columns 3 through 6. Starting from column 8, you can specify the node-name or node-number. Optionally, you can include a delimiter parameter, preceded by a blank, if desired. It's important not to continue an /*XMIT statement beyond the specified format.

JCL XMIT Usage Example.

Here are a few examples demonstrating the usage of the /*XMIT statement in different scenarios:

Example 1: Transmitting from JES2 to another node

//RU0001T JOB (00034),’RC’,CLASS=A,
JES2 /*XMIT node-name,DLM=XX
JES3 //*XMIT DEST=node-name,DLM=XX,SUBCHARS=YY
JCL // XMIT DEST=node-name,DLM=XX,SUBCHARS=YY only in JES3
Lines if data
/*

The Parameter is as follows : 

  • Node-name: names the node to which data need to be sent.
  • DLM=XX: is optional and changes the delimiter character from /* to two characters you specify.
  • SUBCHARS= YY: is also optional and specifies replacement characters to be used for the first two characters of any /*EOF or /*DEL internal reader control statement that is transmitted as lines of data so that they will not be executed.

Question 1: What is the JCL XMIT statement?

The JCL XMIT statement is a powerful feature in JCL (Job Control Language) that facilitates the transmission of data or jobs from one JES (Job Entry Subsystem) or non-JES node to another. It allows users to send data streams or job input streams, along with associated Job Control Language (JCL), to a target node for processing.

Question 2: How do I use the JCL XMIT statement?

To use the JCL XMIT statement, you need to include it in your JCL code. The statement starts with /*XMIT, followed by the necessary parameters such as node-name or node-number. Optionally, you can include additional parameters like the delimiter (DLM) parameter to specify a custom delimiter for the transmission. It is important to ensure that the transmitted input stream adheres to the required format at the destination node.

Question 5: What are some common errors that can occur when using the JCL XMIT statement?

When using the JCL XMIT statement, it is important to ensure proper syntax and adherence to the requirements of the target node. Common errors that can occur include:
  • Missing or incorrect node-name or node-number parameter.
  • Improper usage or placement of the /*XMIT statement within the JCL code.
  • Incompatible JCL or data formats between the transmitting and receiving nodes.
  • Failure to specify the appropriate delimiter or using an invalid delimiter.
  • To avoid these errors, carefully review the JCL code and verify compatibility between the transmitting and receiving nodes, ensuring adherence to the required format and parameters.

Question 6: What is the JCL XMIT Statement and How to Use It?

The JCL XMIT statement is a crucial feature in Job Control Language (JCL) that enables efficient data transmission between different JES (Job Entry Subsystem) or non-JES nodes. By utilizing the XMIT statement, users can easily send data streams or job input streams, including associated JCL, from one node to another.

Summary.

The JCL XMIT statement is a powerful feature in Job Control Language (JCL) that enables efficient data transmission between JES (Job Entry Subsystem) and non-JES nodes. The XMIT statement allows users to transmit job input streams or data streams to target nodes, facilitating seamless data exchange. Understanding the syntax and correct implementation of the XMIT statement is crucial to ensure successful data transmission. By leveraging the capabilities of the XMIT statement, users can enhance their data transmission processes and optimize the efficiency of their JCL workflows.

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