What is Smon process in Oracle?
The system monitor process (SMON) performs recovery, if necessary, at instance startup. SMON is also responsible for cleaning up temporary segments that are no longer in use and for coalescing contiguous free extents within dictionary managed tablespaces.
What is Smon and Pmon in Oracle?
PMON and SMON are two required background processes. PMON is the Process Monitor which is responsible for recovering processes when the user process fails. PMON does the process cleanup. SMON is the System Monitor which is responsible for recovering the system after a failure.
How does Smon perform instance recovery?
As long as one instance continues running, its SMON process performs instance recovery for any other instances that fail. If all instances of an Oracle Parallel Server fail, instance recovery is performed automatically the next time an instance opens the database.
What is instance recovery in Oracle?
Instance recovery refers to the case where a surviving instance recovers a failed instance in an Oracle Real Application Clusters database. The goal of crash and instance recovery is to restore the data block changes located in the cache of the dead instance and to close the redo thread that was left open.
What is the purpose of Smon?
SMON (System MONitor) is an Oracle background process created when you start a database instance. The SMON process performs instance recovery, cleans up after dirty shutdowns and coalesces adjacent free extents into larger free extents. SMON wakes up every 5 minutes to perform housekeeping activities.
Which of the following is the purpose of the Smon background process?
What is the purpose of SMON (System Monitor Process) background process? Explanation: SMON process of one instance can perform instance recovery for a failed CPU or instance.
Which tasks are accomplished by the Smon process?
SMON is the System Monitor and, among other things, performs instance recovery, cleans up the database transactions, and tidies up space utilization.
Which background process does instance recovery?
The SMON background process performs instance recovery, and applies the changes from the redo logs (rolls forward all the changes). In the first phase of the instance recovery, all the changes from the redo logs are applied by SMON.
What is roll forward and roll backward Oracle?
Roll forward occurs during database, tablespace or datafile recovery and during crash recovery. Rollback is the process of undoing uncommitted database transactions. The blocks copied to the rollback segments during transactions as a copy of the block for other transaction to read.
What are the types of recovery in Oracle?
There are three basic types of recovery: instance recovery, crash recovery, and media recovery. Oracle performs the first two types of recovery automatically at instance startup; only media recovery requires you to issue commands.
What is the phases of instance recovery?
Instance and crash recovery occur in two phases. In phase one, Oracle applies all committed and uncommitted changes in the redo log files to the affected datablocks. In phase two, Oracle applies information in the rollback segments to undo changes made by uncommitted transactions to the data blocks.
What is redo log buffer in Oracle?
The most crucial structure for recovery operations is the redo log, which consists of two or more preallocated files that store all changes made to the database as they occur. Every instance of an Oracle Database has an associated redo log to protect the database in case of an instance failure.
Which process reads data from datafiles?
Reading is Always done by Oracle server Process and Writing the Data from Buffer Cache to Disks is done by DBWR Process.
Which process reads data from datafiles in Oracle?
What is roll forward transaction?
What Is Roll Forward? Roll forward refers to extending the expiration or maturity of an option, futures contract, or forward by closing the initial contract and opening a new longer-term contract for the same underlying asset at the then-current market price.
How instance recovery happens in Oracle RAC?
Instance recovery occurs when an instance goes down abruptly, either via a SHUTDOWN ABORT, a killing of a background process, or a crash of a node or the instance itself.