The
log writer process
(LGWR) is responsible for redo log buffer management—writing the redo log buffer to a redo log file on disk. LGWR writes all redo entries that have been copied into the buffer since the last time it wrote.
What is the purpose of Ckpt?
CKPT (Oracle Checkpoint Process) is
an Oracle background process that timestamps all datafiles and control files to indicate that a checkpoint has occurred
. The “DBWR checkpoints” statistic (v$sysstat) indicates the number of checkpoint requests completed.
What is the use of Pmon in Oracle?
The process monitor (PMON)
monitors the other background processes and performs process recovery when a server or dispatcher process terminates abnormally
. PMON is responsible for cleaning up the database buffer cache and freeing resources that the client process was using.
Why Lgwr writes before Dbwr?
Log writer process (LGWR)
writes redo entries after certain amount of time to ensure that free space is available for new
redo entries. The Log Writer (LGWR) writes contents from the Redo Log Buffer to the Redo Log File that is in use.
When a transaction is committed what does the Lgwr do?
Whenever a transaction is committed, LGWR
writes the transaction redo records from the redo log buffer of the SGA to a redo log file
, and assigns a system change number (SCN) to identify the redo records for each committed transaction.
Where Lgwr process writes information?
Log Writer Process (LGWR) The log writer process (LGWR) is responsible for redo log buffer management—writing the redo log buffer to
a redo log file on disk
. LGWR writes all redo entries that have been copied into the buffer since the last time it wrote.
What is ARCn process?
Archiver processes (ARCn) are
background processes that exist only when the database is in archivelog mode and automatic archiving is enabled
. … you can have up to ten archiver processes running for a single instance in Oracle.
How do I know if Pmon is running?
On Windows systems, go
to Control Panel→Administrative Tools→Services
to see whether the Oracle service has started. You can also look under Windows Task Manager to find similar information. On Linux/UNIX systems, simply check for the PMON process. Without PMON, there’s no Oracle database instance running.
What is a tablespace in Oracle?
An Oracle database consists of one or more logical storage units called tablespaces,
which collectively store all of the database’s data
. Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that conform to the operating system in which Oracle is running.
What is a listener in Oracle?
The Oracle listener is
a service that runs on the database host and receives requests from Oracle clients
. Sometimes the listener forwards requests to the database server (Figure 8.3), and sometimes it redirects the client somewhere else where the database server listens for dedicated connections (Figure 8.4).
When did Lgwr write to log files?
LGWR writes redo log entries into an on-line redo log file
when transactions commit and the log buffer files are full
.
What is dirty buffer in Oracle?
A dirty buffer is
a buffer whose contents have been modified
. Dirty buffers are freed for reuse when DBWR has written the blocks to disk. The database buffer cache is organized in two lists: the write list and the least-recently-used (LRU) list.
What is MMON process in Oracle?
MMON (Manageability Monitor) is
a background process that gathers memory statistics (snapshots) and stores this information in the AWR
(automatic workload repository). MMON is also responsible for issuing alerts for metrics that exceed their thresholds. This process was introduced in Oracle 10g.
What determines the best possible way to execute a query?
Oracle optimizer
determines the best possible way to execute a query. The query optimizer (called simply the optimizer) is a built-in database software that determines the most efficient method for a SQL statement to access requested data.
What is redo log file in Oracle?
What Is the Redo Log? 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 is responsible for Signalling DBWn at checkpoints?
When a checkpoint occurs,
the log writer process (LGWR)
signals DBWn and DBWn writes all buffers that need to be written for the checkpoint to complete.
