The DevOps Code ClearCase scheduler

The scheduler’s work is defined in terms of jobs and tasks.

• A job is a data structure that defines the execution schedule for a task and stores any exit status associated with the most recent execution of the task. Each job runs a single task.
• A task is an executable program or script. A task may be run by more than one job and, because a job can pass job-specific arguments to a task, the operations performed by a task can be customized to suit the schedule on which the job runs the task.

Unlike the general-purpose scheduled-execution utilities (cron, at, ...) associated with the operating systems on which DevOps Code ClearCase runs, the scheduler is integrated with the DevOps Code ClearCase management infrastructure and supports these functions:

• Centralized management with cleartool or the DevOps Code ClearCase Administration Console
• Access control based on user and group identity
• Flexible scheduling based on time of day, period, or execution of another task
• A default set of tasks and jobs that run on every host
• Additional tasks and jobs that can be enabled when appropriate for a given host
• Custom tasks and jobs

The scheduler is managed by the albd_server. The schedule program is an interface to the job and task registries that provide the scheduler with work to do. A small set of tasks and jobs run by default on all systems. Others must be specifically enabled when appropriate. To modify jobs or tasks, take one or more of the following steps:

• Modify the scheduler access control list (ACL), if necessary.
• Add jobs to the default daily and weekly local tasks
• Define new tasks and jobs for them to run.