I'm aware of the links that are shared. In the guide, there is no mentioned about the memory partition we need have, but giving whole disk space generically as minimum 18 GB. But my question is: out of allocated Hard disk, how much memory space must be allocated (partitioned) for /opt, /var and /log so that IDQ 10.4 will run smoothly?
By default, an IDQ installation will place everything within the Informatica home location so if installing to /opt with defaults, /var & /log will not be used.
18gigs is the bare minimum that Informatica recommends. Now realistically how much disk space you will need depends on what you are using IDQ for. Are you using IDQ for data movement (ETL), are you using DQ for data profiling and scorecarding, human task, web services.............the factors of giving you a recommendation are too large to just say here are the numbers. it also depends if anything else is running on the same machine using those directories. most installations have a INFA home of over 50GB but yours could 1TB depending on what you are doing.
Sorry don't have a concrete answer.