@Nanda 

Apologies for the delayed reply. The answer to your question is: unless you choose to delete all snapshots for the VM, changes to the base disk will not be committed.

Please let me know if that answers your question.

@Nanda  On the top of what was mentioned by @Alona 

Say we created three snapshots and deleted a second snapshot which have new data written while the base vDisk was read only, what happens to the newly written data?

Before you remove the second snapshot all the “newly written” data on it will have been inherited by the third snapshot and will be available on it;  so deleting the second snapshot won’t delete any new data that was written on it when it was not read only.

But the old data on the second snapshot where they were “overwritten” on the third snapshot will be lost (forever, if you do not take a clone of the second snapshot before deleting it). 

And as was mentioned, all data will be committed to the base disk when all the snapshots are removed

Hope this clarifies further.

-Said