Here are some tips for improving performance.
Always update to the latest patch. We continually improve performance with each update.
If you start experience framerate and performance issues, save your game. Restart your Playstation 3 and reload the save. If the performance issues persist, here are other things to try.
Turn off auto saves. This can cause temporary stuttering since the PS3 saves these files in the background
This is most noticeable with large saves when fast traveling to a new area or entering a new area that auto saves.
Waiting for time to pass. Many things are running in the world depending on what quests you've done or places you have visited. Using Wait or Rest options, passing time will clear up some of these. It depends how long you wait, it may take up to 30 days for some items. Saving, resetting, and loading after this will have the largest effect.
Save your game and restart your Playstation 3 during long play sessions (6 hours or more).
If your game is freezing when entering water, make sure you’ve updated to the latest patch.
If you’ve updated to the latest patch and you encounter strange behavior immediately following application of the patch including queued messages appearing on the screen, just wait and let this process run its course. This is a temporary effect of certain Skyrim scripts correcting themselves after the update. Once this process is complete, make a new save and restart your Playstation 3.
Clear space on your hard drive. Clearing at least 2 or more GB of space for best results. Skyrim makes heavy use of the hard drive, and freeing up space on here seems to help many people. Hard drive speeds also differ in PS3 models. Some users have reported increase performance by upgrading their drives.
The PS3’s Safe Mode* feature includes options that can help with memory fragmentation.
Restore File System. Attempts to repair all areas on the hard disk drive where files can be saved. Corrupted data may be erased, which can help performance.
If you choose not to enter Safe Mode, you can manually delete corrupted saves within the XMB menu. Go to Games>Saved Game Utility. Within the menu, delete any corrupted save files. These files can be created from Skyrim and other games when a game doesn’t save properly (shutting down the console before an autosave completes, etc).
Rebuild Database. Will help with memory fragmentation on the PS3 HDD. Note: Using Rebuild Database will erase messages, playlists, changes made on [Information] screens, trimming information for pictures in [Photo], video thumbnails, video playback history and video resume information. The content that is erased will not be recoverable.
*Sony does not recommend using the options in Safe Mode unless you are experiencing issues with the PlayStation 3. Some of these options could result in loss of data.