Status control bits in the sysdatabases table

Decimal                       Hex                             Status

4                                  0x04                            select into/bulkcopy; can be set by user

8                                  0x08                            trunc log on chkpt; can be set by user

16                                0x10                            no chkpt on recovery; can be set by user

32                                0x20                            Database created with for load option, or crashed while loading database, instructs recovery not to proceed

256                              0x100                          Database suspect; not recovered; cannot be opened or used; can be dropped only with dbcc dbrepair

512                              0x200                          ddl in tran; can be set by user

1024                            0x400                          read only; can be set by user

2048                            0x800                          dbo use only; can be set by user

4096                            0x1000                        single user; can be set by user

8192                            0x2000                        allow nulls by default; can be set by user

There is also an undocumented value which is 320, this is very similar to 256 i.e. database suspect, but it allows you to perform certain functions on the db.