unable to start ORACLE database My application is running on Oracle Database which hosts 3 database instances. All of sudden one of my database instance is not running. when connected through sysdba it says "connected to idle instance". Here are the activities performed

Oracle version:Release 11.2.0.4.0


sudo su - oracle
export ORACLE_SID=testdev1
sqlplus / AS SYSDBA



  Connected to an idle instance.



shutdown immediate



  ORA-01034: ORACLE not available
  
  ORA-27101: shared memory realm does not exist Linux-x86_64 Error: 2:
  No such file or directory



startup



  ORA-01078: failure in processing system parameters
  
  ORA-01565: error in identifying file
  '+DATADG/testdev1/spfiltestdev1.ora' 
  
  ORA-17503: ksfdopn:2 Failed to open file
  +DATADG/testdev1/spfiletestdev1.ora
  
  ORA-29701: unable to connect to Cluster Synchronization Service


can anyone help me what is the issue ?
unfortunately my database ASM service is not running. I restarted and everything worked. thanks all for your help