Instance
ü Memory (SGA) + Background Process
Instance (Database) Startup stages
ü NOMOUNT -> MOUNT -> OPEN
Stage1: STARTUP NOMOUNT
Step1: Reads Parameter File (Location: $ORACLE_HOME/dbs)
Step2: Allocates SGA
Step3: Start the Background Process
ORACLE_HOME
ü Location where the oracle software is installed
Parameter File types
ü PFILE
ü SPFILE (Server Parameter File)
Note:
ü Oracle gives the first preference to the SPFILE
ü If SPFILE is not available then oracle gives the second preference to the PFILE
Stage2: MOUNT
Step1: It reads the Control file & Identifies Database Name, Location of Data files & Redo log files
Step2: It connects the Instance (Logical) to the Database (Physical)
Stage3: OPEN
Step1: It physically checks the presence of Data & Redo Log Files
Step2: It compares the SCN in Data, Control & Redo Log Files
Instance (Database) Shutdown stages
ü Database (Closed) -> Database (Dismounted) -> Instance (shutdown)
SHUTDOWN Options
ü NORMAL (Recommended)
ü TRANSACTIONAL
ü IMMEDIATE
ü ABORT
ü FORCE
SHUTDOWN NORMAL or SHUTDOWN
Step1: No new user connections are allowed
Step2: All dirty buffers will be written to data files
Step3: All redo log buffers will be written to redo log files
Step4: It synchronizes the SCN in data, control and Redo log files
Step5: All background process will be terminated
Step6: Database is dismounted
Step7: Release the SGA
Step8: Instance is shutdown
Note:
When we startup the database next time no recovery is required (Since SCN matches in all the files)
SHUTDOWN TRANSACTIONAL
Step1: No new user connections are allowed
Step2: It waits until the current transaction is completed
Step3: All dirty buffers will be written to data files
Step4: All redo log buffers will be written to redo log files
Step5: It synchronizes the SCN in data, control and Redo log files
Step6: All background process will be terminated
Step7: Database is dismounted
Step8: Release the SGA
Step9: Instance is shutdown
Note:
When we startup the database next time no recovery is required (Since SCN matches in all the files)
SHUTDOWN IMMEDIATE
Step1: No new user connections are allowed
Step2: No new transactions are allowed
Step3: It rollbacks uncommitted transactions & does not wait for the transaction to be completed
Step4: All dirty buffers will be written to data files
Step5: All redo log buffers will be written to redo log files
Step6: It synchronizes the SCN in data, control and Redo log files
Step7: All background process will be terminated
Step8: Database is dismounted
Step9: Release the SGA
Step10: Instance is shutdown
Note:
When we startup the database next time no recovery is required (Since SCN matches in all the files)
SHUTDOWN ABORT
Step1: It immediately crashes the Instance
Step2: Dirty buffers are not written to data files
Step3: Redo log buffers are not written to redo log files
Step4: No synchronization of SCN in data, control and Redo log files
Note:
When we startup the database next time it requires recovery (Since SCN does not matches in all the files)
STARTUP FORCE = SHUT ABORT + STARTUP
