xJCL elements

Network Deployment (Distributed operating systems), v8.0 > Develop and deploying applications > Develop batch applications > Submit batch jobs

xJCL elements

Jobs are expressed using an Extensible Markup Language XML dialect called xJCL (XML Job Control Language). This dialect has constructs for expressing all of the information needed for both compute-intensive and batch jobs, although some elements of xJCL are only applicable to compute-intensive or batch jobs. See the xJCL provided with the Sample applications, the xJCL table, and xJCL XSD schema file for more information about xJCL. The xJCL definition of a job is not part of the batch application, but is constructed separately and submitted to the job scheduler for to run. The job scheduler uses information in the xJCL to determine where and when to run the job.

xJCL elements

The following table summarizes the xJCL elements.

xJCL elements. The table includes xJCL elements, whether each xJCL element applies to compute-intensive or batch jobs, and subelements, attributes, and descriptions for each xJCL element.

Element Java EE Compute- intensive Java EE Batch Subelement Attributes Description
job Y Y Scopes the description of a batch job.
job Y Y name Name of the job. This name must match the name of the batch application
job Y Y accounting Optional accounting information attribute.
job Y Y class Optional job class attribute, which identifies the job class under which the job runs.
job Y Y default-application-name New feature: The application name to be used when no job step application-name attribute is found.
job Y Y jndi-name JNDI name that is given to the job controller stateless session bean when the batch application is deployed into WAS.
job Y Y job-scheduling criteria required-capability The required-capability of the job, which must be defined on an endpoint for the job to be dispatched to that endpoint.
job Y Y step-scheduling criteria See step-scheduling-criteria element
job N Y checkpoint algorithm See checkpoint-algorithm element
job N Y results-algorithm See results-algorithms element
job Y Y substitution-props++ See prop element The required-capability of the job, which must be defined on an endpoint for the job to be dispatched to that endpoint
job-step Y* Y name Optional name of the step. This information is returned on operational commands.
job-step Y* Y application-name Optional name of the application run by the step. The attribute name is used if application-name is omitted and the job level attribute default-application-name is omitted.
job-step N Y step-scheduling See step-scheduling element Allows for conditional logic based on return codes of steps that determines whether the batch step is invoked.
job-step Y Y classname Fully-qualified name of class that implements the compute intensive job.
job-step Y N checkpoint-algorithm-ref Checkpoint algorithm to use for the batch job step.
job-step N Y results-ref See results-ref element Results algorithm to use for the conditional batch job step execution.
job-step N Y batch-data-streams See batch-data-streams element A sequence of bds elements. Each bds is the configuration information necessary to create a batch data stream.
job-step Y Y props See props element Name-value properties to pass to the step.
job-step N N exec See exec element Identifies the executable associated with the job step.
job-step N N env-entries See env-entries element Identifies the environmental properties associated with the job step.
prop Y Y Single instance of a name pair, that serves as a property.
prop Y Y name Name of the property.
prop Y Y value Value of the property.
props Y Y prop See prop element
env-entries N N Series of prop elements that are used to pass name-value pair properties to steps, bds, checkpoint algorithms, and results algorithms.
env-entries N N env-var See env-var element
exec N N Series of prop elements that are used to pass name-value pair properties to steps, bds, checkpoint algorithms, and results algorithms.
exec N N executable The name of the executable associated with the job step.
exec N N arg See line element
line N N Command-line arguments passed to the job step executable.
bds N Y Single instance of a batch data stream implementation made available to the batch job.
bds N Y logical-name A string that is embedded in batch step, which uses it to query the batch runtime environment for a specific batch data stream instance.
bds N Y impl-class Fully- qualified class name of the batch data stream implementation class.
bds N Y props See props elements List of properties that are passed to the batch data stream implementation class.
batch-data-streams N Y Series of bds elements
batch-data-streams N Y bds See bds element
step-scheduling N Y Applies to job-steps to create return code-based conditional flows for a batch job. Compares values of return codes defined for this batch job to decide whether a step is invoked or not while processing a batch job. The values of return codes are compared using the returncode-expression element.
step-scheduling N Y returncode- expression see returncode-expression Returncode- expression to evaluate.
step-scheduling N Y condition If there is more than one returncode-expression element in the step-scheduling element, conditional operators are applied to them. Conditional operators supported are: AND, OR.
returncode-expression N Y Used under step-scheduling tags to decide whether a batch job step runs based on return codes of other job steps.
returncode-expression N Y step Name of step whose return code is to be compared in this expression.
returncode-expression N Y operator Operator to use for the return code expression. The supported operators are eq for equals, lt for less than, gt for greater than, le for less than or equal to, and ge for greater than or equal to.
returncode-expression N Y value The value with which to compare the return code.
step-scheduling-criteria N Y Describes the sequence in which the job steps are processed. Currently sequential scheduling is supported; for example, steps get invoked in the order in which they exist in xJCL.
step-scheduling-criteria N Y scheduling-mode Sequence in which to invoke steps, only possible value is sequential right now.
checkpoint-algorithm N Y Declares a checkpoint algorithm that can be used for a batch job step.
checkpoint-algorithm N Y name Name of algorithm.
checkpoint-algorithm N Y classname Class that implements this algorithm.
checkpoint-algorithm N Y props See props element Sequence of prop elements for the checkpoint algorithm.
checkpoint-algorithm-ref N Y Reference to a checkpoint algorithm element.
checkpoint-algorithm-ref N Y name Name of checkpoint algorithm to which you are referring.
checkpoint-algorithm-ref N Y props See props element. Sequence of prop elements for the checkpoint algorithm.

++ The xJCL element substitution-props is discussed in the following section.

xJCL substitution-props

The job xJCL can contain symbolic variables. A symbolic variable is an expression of the form ${variable-name}, which is found outside a comment in an otherwise well-formed document. For example:
<checkpoint-algorithm-ref name="${checkpoint}" /> 
The xJCL element, substitution-props, defines a default name and value pairs for symbolic variables. Following is an example of the substitution-props element, taken from the postingSampleXJCL.xml document:
<substitution-props>
<prop name="wsbatch.count" value="5" />

<prop name="checkpoint" value="timebased" />
<prop name="checkpointInterval" value="15" />
<prop name="postingsDataStream" value="${was.install.root}${file.separator}temp${file.separator}postings" />
</substitution-props> 
Substitution for symbolic variables occurs at run time. At run time, the string ${variable-name} is replaced with the value of the property when the xJCL is submitted for execution. Using the properties in the previous example, the string ${checkpoint} is replaced with the string time-based before the job is submitted.
Symbolic variables can be indirect. For example: name=FILENAME value=${${filename}} used with the name/value pair filename=postingsDataStream yields the same result as specifying name=FILENAME value=${postingsDataStream}.
Symbolic variables can also be compound. For example, name=postingsDataStream value=${was.install.root}${file.separator}temp${file.separator}postings.
The name/value pairs do not have to be defined in the job document substitution-props element. The props name and value pairs defined in the substitution-props element are default values for the named variables. If not defined in the substitution-props element, name/value pairs must be either passed in via the job scheduler APIs when the job is submitted or defined in the system properties for the JVM. Every symbolic variable defined in the body of a job document must be resolved for the xJCL to be considered valid. Every name/value pair defined in the job document must resolve to a symbolic variable which is found in the body of the xJCL for the xJCL to be considered valid.
If name/value pairs are both defined in the xJCL document and passed to the job scheduler APIs at job submission time, the name/value pairs passed via the Job Scheduler APIs override the default values defined in the xJCL document. If name/value pairs are neither passed in via the job scheduler APIs nor defined as defaults in the xJCL document, name/value pairs for the symbolic variables must be defined in the system JVM properties for the xJCL to be considered valid.
Symbolic variables are resolved by the job scheduler before job submission, except for the following special variables, which are resolved at the grid endpoint. The following special variables all must be defined as JVM system properties. They are:

${was.install.root}
${user.install.root}
${agent.home}

XML schema for a batch job
xJCL sample for a batch job

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Element	Java EE Compute- intensive	Java EE Batch	Subelement	Attributes	Description
job	Y	Y			Scopes the description of a batch job.
job	Y	Y		name	Name of the job. This name must match the name of the batch application
job	Y	Y		accounting	Optional accounting information attribute.
job	Y	Y		class	Optional job class attribute, which identifies the job class under which the job runs.
job	Y	Y		default-application-name	New feature: The application name to be used when no job step application-name attribute is found.
job	Y	Y	jndi-name		JNDI name that is given to the job controller stateless session bean when the batch application is deployed into WAS.
job	Y	Y	job-scheduling criteria	required-capability	The required-capability of the job, which must be defined on an endpoint for the job to be dispatched to that endpoint.
job	Y	Y	step-scheduling criteria	See step-scheduling-criteria element
job	N	Y	checkpoint algorithm	See checkpoint-algorithm element
job	N	Y	results-algorithm	See results-algorithms element
job	Y	Y	substitution-props++	See prop element	The required-capability of the job, which must be defined on an endpoint for the job to be dispatched to that endpoint
job-step	Y*	Y		name	Optional name of the step. This information is returned on operational commands.
job-step	Y*	Y		application-name	Optional name of the application run by the step. The attribute name is used if application-name is omitted and the job level attribute default-application-name is omitted.
job-step	N	Y	step-scheduling	See step-scheduling element	Allows for conditional logic based on return codes of steps that determines whether the batch step is invoked.
job-step	Y	Y	classname		Fully-qualified name of class that implements the compute intensive job.
job-step	Y	N	checkpoint-algorithm-ref		Checkpoint algorithm to use for the batch job step.
job-step	N	Y	results-ref	See results-ref element	Results algorithm to use for the conditional batch job step execution.
job-step	N	Y	batch-data-streams	See batch-data-streams element	A sequence of bds elements. Each bds is the configuration information necessary to create a batch data stream.
job-step	Y	Y	props	See props element	Name-value properties to pass to the step.
job-step	N	N	exec	See exec element	Identifies the executable associated with the job step.
job-step	N	N	env-entries	See env-entries element	Identifies the environmental properties associated with the job step.
prop	Y	Y			Single instance of a name pair, that serves as a property.
prop	Y	Y		name	Name of the property.
prop	Y	Y		value	Value of the property.
props	Y	Y	prop	See prop element
env-entries	N	N			Series of prop elements that are used to pass name-value pair properties to steps, bds, checkpoint algorithms, and results algorithms.
env-entries	N	N	env-var	See env-var element
exec	N	N			Series of prop elements that are used to pass name-value pair properties to steps, bds, checkpoint algorithms, and results algorithms.
exec	N	N		executable	The name of the executable associated with the job step.
exec	N	N	arg	See line element
line	N	N			Command-line arguments passed to the job step executable.
bds	N	Y			Single instance of a batch data stream implementation made available to the batch job.
bds	N	Y	logical-name		A string that is embedded in batch step, which uses it to query the batch runtime environment for a specific batch data stream instance.
bds	N	Y	impl-class		Fully- qualified class name of the batch data stream implementation class.
bds	N	Y	props	See props elements	List of properties that are passed to the batch data stream implementation class.
batch-data-streams	N	Y			Series of bds elements
batch-data-streams	N	Y	bds	See bds element
step-scheduling	N	Y			Applies to job-steps to create return code-based conditional flows for a batch job. Compares values of return codes defined for this batch job to decide whether a step is invoked or not while processing a batch job. The values of return codes are compared using the returncode-expression element.
step-scheduling	N	Y	returncode- expression	see returncode-expression	Returncode- expression to evaluate.
step-scheduling	N	Y		condition	If there is more than one returncode-expression element in the step-scheduling element, conditional operators are applied to them. Conditional operators supported are: AND, OR.
returncode-expression	N	Y			Used under step-scheduling tags to decide whether a batch job step runs based on return codes of other job steps.
returncode-expression	N	Y		step	Name of step whose return code is to be compared in this expression.
returncode-expression	N	Y		operator	Operator to use for the return code expression. The supported operators are eq for equals, lt for less than, gt for greater than, le for less than or equal to, and ge for greater than or equal to.
returncode-expression	N	Y		value	The value with which to compare the return code.
step-scheduling-criteria	N	Y			Describes the sequence in which the job steps are processed. Currently sequential scheduling is supported; for example, steps get invoked in the order in which they exist in xJCL.
step-scheduling-criteria	N	Y	scheduling-mode		Sequence in which to invoke steps, only possible value is sequential right now.
checkpoint-algorithm	N	Y			Declares a checkpoint algorithm that can be used for a batch job step.
checkpoint-algorithm	N	Y		name	Name of algorithm.
checkpoint-algorithm	N	Y	classname		Class that implements this algorithm.
checkpoint-algorithm	N	Y	props	See props element	Sequence of prop elements for the checkpoint algorithm.
checkpoint-algorithm-ref	N	Y			Reference to a checkpoint algorithm element.
checkpoint-algorithm-ref	N	Y		name	Name of checkpoint algorithm to which you are referring.
checkpoint-algorithm-ref	N	Y	props	See props element.	Sequence of prop elements for the checkpoint algorithm.