ORA-10873:file 1 needs to be either taken out of backup mode or media recovered ORA-01110: data file 1: '+DATA / testbk/ datafile/ system.256.897496663'

ORA-10873:file 1 needs to be either taken out of backup mode or media recovered  ORA-01110: data file 1: '+DATA / testbk/ datafile/ system.256.897496663'

Cause: ORA-10873
In case you force fully trying to shutdown database with “shutdown abort” OR instance crashes for some reason OR database have not been shutdown gracefully than you would encountered “ORA-10873” error while next startup of your database.

SQL> startup
ORACLE instance started.

Total System Global Area 5127602176 bytes
Fixed Size                  2214432 bytes
Variable Size            4580181472 bytes
Database Buffers          536870912 bytes
Redo Buffers                8335360 bytes
Database mounted.
ORA-10873: file 1 needs to be either taken out of backup mode or media recovered
ORA-01110: data file 1: '+DATA/testbk/datafile/system.256.897496663'

Solution:  Issue following SQL command in order to move out database from hot backup mode:
SQL> alter database end backup;
alter database end backup
*
ERROR at line 1:
ORA-01260: warning: END BACKUP succeeded but some files found not to be in
backup mode

OR

SQL> alter tablespace system end backup;

Open database
SQL> alter database open;
Database altered.