When the job scheduler accepts a job, it creates the job’s PCB (Process Control Blocks) and updates it throughout the execution.
These PCBs, and not the jobs, are linked to form the queues and are used to track the respective jobs.
The PCB store all of the data about the job being processed, like it’s progress in the system. This data is needed by the operating system to manage the processing of the job.
As shown above, each queue can be seen as the linked list of PCBs:
- READY queue contains PCBs for ready jobs.
- HOLD queue contains PCBs for the jobs entering the system.
- WAITING queue contains PCBs for the jobs which need some resource allocation or input from the user. Depending upon their reason to be in the WAITING queue, they are linked into several queues. E.g., The PCBs waiting for some input are in a separate queue, while asking for determining the file location of a specific file is in a separate queue.
WAITING queues are managed in a specific order according to some policies.
- Process Scheduler : Job and Process Status
- Difference between dispatcher and scheduler
- Difference between Long-Term and Short-Term Scheduler
- Pass the value from child process to parent process
- Process states and Transitions in a UNIX Process
- Process Table and Process Control Block (PCB)
- TCP 3-Way Handshake Process
- Process Synchronization | Set 2
- Reversal process in DFA
- Complementation process in DFA
- Concatenation process in DFA
- Union process in DFA
- Communication between two process using signals in C
- Get/Set process resource limits in C
- Difference between Process and Thread
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