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Tuesday, February 9, 2016

Suspend and Resume in Oracle Database

The ALTER SYSTEM SUSPEND  statement stops all  input  and  output  (I/O)  to  datafiles (file header and file data)  and  control files. The  suspended  state  lets  us  back  up  a database  without  I/O interference. When  the database  is suspended  all  preexisting I/O operations are  allowed  to complete and any  new  database  accesses  are  placed  in a  queued state. The  suspend   command is  not  specific  to  an  instance. In  an  Oracle  Real  Application  Clusters  environment, when  we issue the  suspend command  on  one  system,  internal  locking  mechanisms  propagate  the  halt request across  instances, thereby quiescing all active instances  in  a  given cluster. However, if someone starts  a  new instance another instance is being suspended, the new instance will not be suspended .

ALTER SYSTEM RESUME  statement resumes normal database operations. The SUSPEND and  RESUME commands  can  be  issued  from  different  instances. For example, if instances 1, 2, and 3 are  running, and  we  issue  an  ALTER SYSTEM  SUSPEND  statement  from  instance 1, then  we  can issue  a RESUME  statement from instance 1, 2, or 3 with the same effect.

The  suspend/resume  feature is  not a  suitable  substitute  for  normal  shutdown  operations, because  copies  of a  suspended  database can  contain  uncommitted  updates.

To check

SQL> alter system suspend;
System altered

SQL> select database_status  from v$instance;


SQL> alter system resume ;
System altered

SQL> select database_status from v$instance ;


1 comment:

Sridevi K said...

Sridevi Koduru (Senior Oracle Apps Trainer
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