You may have seen various games such a GTA San Andreas, Max Payne, Bully, and many many more that have been ported over to the Vita. When a game is 'Ported' it means that a game that was originally designed and created for one device (such as PC) has been adapted to work on another system, in our case the Vita
I will say from the start that game ports are not always guaranteed to work perfectly without any strange issues, missing items or textures, random crashing or glitching and many other possible issues. The creators of the ports have often spent multiple hours rewriting code and more to get these to work in the first place so the fact that they run at all is always impressive, but dont expect a perfection and respect the work.
Why does my game not work?
In brief :
The VPK file you installed of a port doesnt contain the game data
You need to source and add the game data yourself
You may need a libshaccc file if you dont already
You may need the FD_Fix and KU_Bridge plugins installing
You may not have the game data in the correct location
The game may just have issues
In more details :
Many people dont understand or realise that when they install a game port VPK (usually from VitaDB), that this is NOT the actual game but in more basic terms, its a launcher for the game. for example the GTASA.vpk is less than 2Mb (Megabytes) and the needed 'Android' data files are over 2Gb (Gigabytes)
In most cases you will need the actual game files for the port from a specific version of the game and add them the correct location on your Vita. Depending on the game port this will be from either the PC version or Android version of the game.
Officially the data files should always come from your OWN PURCHASED COPY of the game but Unofficially they can be downloaded and found with a bit of google searches or Youtube videos
If you have installed VitaDB then you will already have the required libshaccc.suprx file and wont see the error but if you dont have the file then the easiest method is to just install and run VitaDB. this will update your PSN Runtime and extract the file. After installing and running VitaDB you can then delete SharkF00d.
Quite a few ports require the KU_Bridge and FD_Fix plugins. The easiest way to install these is by installing and running Autoplugin2, selecting install vita plugins, then find and install the 2 plugins.
The data files are 'usually' required in UX0:DATA/ but always make sure to read the ports requirements and double check where your putting the files. for example the data files for GTASA are required in
UX0:DATA/GTASA/*data files*
but I have seen it plenty of times where people have mistakenly put the GTASA folder into a GTASA folder so the files ended up somewhere like
UX0:DATA/GTASA/GTASA/*data files*
which is incorrect so READ the requirements and double check where you putting the files
Even with everything in place and your port running you may find that your game has issues such as stuttering, glitchy, crashing, missing graphics, whatever.. game ports are not always 100% complete or compatible so just be happy with whatever you get, praise the developer no harass, and check for updates
GPU CRASH
This issue is more often seen on the 1000 series (phat) but it can show up on any of the devices, its not usually anything to worry too much about even tho it may sound serious and there is no 'FIX' for it as its just a standard crash that you can get with any homebrew app.
You will almost certainly see this with ports such as Bully due to how the game runs and even the port developer says in the read me, that its advised to only play the game in 20 minute sessions at a time.