We have different alerts where it triggers when it will reach the threshold value, there is no such threshold limit for Clipboard. If we keep on increasing the clipbaord size we are degrading the performance of the application.
As has been stated previously, there is no hard limit on clipboard size. However, your system performance - in particular, memory usage - is the limiting factor when approaching this business problem with your proposed solution in mind.
You must consider that if you're storing the file on the clipboard, that means that it's being stored in memory, in the java heap. The associated alerts (50MB by default) are to assist you in determining if BLOBs loaded from the database are growing to unexpected sizes - you can use these to help determine the cause of problems (For example, if you are seeing these alerts, and also seeing garbage collection or out of memory issues, the two are likely correlated.) The configuration settings associated for this alert threshold are detailed here: https://pdn.pega.com/pega0004-alert-quantity-data-received-database-query-exceeds-limit/pega0004-alert-quantity-data
You may need to approach sizing of your java heap with this in mind, for example if you expect to have each requestor store multiple 100MB files in their clipboard, the typical recommendations of 4-8GB heap size may be vastly insufficient for your application. You will also probably need to handle in your own business logic when to remove these large items from the clipboard so that the memory can be recycled and you do not create a memory leak in the application.
You may also want to review the business need for the underlying business process to determine if there's a better way to process your files rather than storing them in the heap.