Resource-Request Algorithm for Process

Let Request i be the request vector for process Pi. If Request [i, j] = k, then process Pi wants k instances of resource type Rj. When a request for resources is made by process Pi, the following actions are taken: 1. If Request i < Need i, go to step 2. Otherwise, raise an error condition, since the process has exceeded its maximum claim. 2. If Request i  Available, go to step 3. Otherwise, Pi must wait, since the resources are not available. 3. Have the system pretend to have allocated the requested resources to process Pj by modifying the state as follows: Available: = Available – Request i; Allocation i := Allocation + Request i; Need i := Need i – Request i; If the resulting Resource-allocation State is safe, the transaction is completed and process Pi is allocated its resources. However, if the new state is unsafe, then Pi must wait for Request i and the old resource-allocation state is restored.