Why all users excep sys and system can connect to oracle db after database deletion on multi database environment? I have 2 database on one server.
I can connect to the database with normal users but cannot connect with sys and system users and invalid username/password occurs. before that I dropped one of the databases and during dropping that database, this error occurred: 


  DIM-00014: cannot open the windows NT service control
  manager.O/S-Error:(OS 5) Access is denied


I check if I can connect sqlplus /nolog and conn / as sysdba and it did not worked and below error occurred:


  12560:  tns protocol adapter error


anybody help!
I finally found a solution. I changed sys password using orapwd. There is just one issue. As documentation says, the password for users which do not have sysdba or sysoper privileges will be expired after some time. So, to avoid this login as sysdba and grant sysdba and sysoper to the sys.