- #Ow to check the back history in dbvisualizer how to
- #Ow to check the back history in dbvisualizer code
In others, monitors area seperate object that controls access to a resource. In some languages, the resources themselves can be made into monitors. They also establish a queue that governs which thread has next access to the resource. Monitors ensure that only one thread at a time can operate on the resource they govern.
#Ow to check the back history in dbvisualizer how to
An early language that made this possible was Algo68.Ī problem that must be solved by all concurrent systems is how to allow simultaneous computations to access the same resources. For example, printing the first page of a graph while the second page was still being processed would save time. The next leap in technology allowed one user to use concurrent computing so that one long computation could run at the same time as one or more others that didn’t depend on the outcome of the long computation. One computation had to wait for another to finish before it could start. An individual user still had to do sequential computing. A language is “concurrent” to the extent that it can safely take advantage of this context switching.Īs computers got fast enough to support virtual memory and fast context switching, it became possible for multiple users to use the same computer system and have the illusion they were the only ones on the system. With multiple processors, this is still true because many more tasks can run than the number of processors. The ability of the processor to switch between tasks fast enough provides an illusion of concurrency. At the processor level, only one task at a time can be performed. If the resources are not managed appropriately, the resources or the threads themselves can become unavailable.Ĭoncurrency is an illusion. Essentially, randomness in outcomes is introduced by the hardware.Ĭoncurrency also introduces situations where resources are requested at the same time by two different threads.
#Ow to check the back history in dbvisualizer code
Concurrency allows them to run in parallel, using system resources more efficiently.Ĭoncurrency introduces indeterminate behavior when computer code executes. Non-concurrent, program statements run one after another. Concurrency allows multiple parts a program to execute at the same time.