There will scheduled PSN Maintenance beginning Wednesday 21st March from 15.00 through till 01.00 on Thursday the 22nd March.
According to a note on the PS Forums, this may not actually affect you from playing online unless you have not signed in for some time, however you will not be able to access the following services:
- PS Store
- Account Management
- Account Registration
We’d imagine this will mean minimum disruption for most.