Is an area of memory that stores data blocks. It improves performance when you run SQL statements. SQL statements are cached as much as possible. No constant IO activities going on.
Note: Everything is stored in Oracle
Is an area of memory that saves changes to database.
Is a place parts of SQL*Plus get's stored. It also stored data dictionary info - metadata infn about d database is stored. It is some place that tells us what tablespaces we have, what views we have, what indexes, what tables we have etc.
When Oracle is passing information around, it is always in block sizes. To find out information about your database block size;
When you set a default block size in your db, you really can't change it.
Note: the 2k, 4k, 16k, 32k buffers are already accounted for in the Buffer cache. So when you are assiging a memory size to a db object, you are doing this in blocks. In addition to our defaut block size, we can have upto 4 additional block sizes (i.e the k buffers - 2k, 4k, 16k, 32k). So u can just easily assign a 2k buffer or 4k buffer to a db object without necessarily directly allocating the memory space on the Buffer cache.
Process monitor. This is used by any user process.
Perform instance recovery especially when you don't shutdown the db properly
Check ur process with ps -ef | grep oracle
A user process is a process that connects to the server process e.g SQLPLUS is a user process. All server processes contains a memory area called the PGA. It contains info about sessions, variable etc.
To see the system db files
To see when a file is created
To query ur redo log files
To query infn about our log group
To add more log files to ur existing group log files
SQL> alter database
add logfile member 'c:\oracle\product\10.2.0\oradata\orcl\redo01b.log'
to group 1
To clear the log file after creation
SQL> alter system switch logfile; // this will create an archive log file
To add a completely new redo log group
SQL> alter database
'c:\oracle\product\10.2.0\oradata\orcl\redo04b.log') size 50m
When you start up a db, you will always have an spfile or init file
To know where ur spfile is
If oracle cannot file any of the files in the category of spfile, then your instance won't startup.
What Oracle does on startup is that it first looks up for SPFILE<ORACLESID>.ORA, if doesn't exist, it looks for spfile.ora, if that doesn't exist, it looks for init.ora and if any of these doesn't exist, then your Oracle won't startup. To locate these files, looks in the dbs directory.
Tells about major event in the db. Trace Files handle session logs. You can find info about alert log files in $ORACLE_HOME/admin/<ORACLE_SID/bdump. You might want to backup this file on a 24 hour basis.
To know where this file is
SQL> show parameter background
Are files that are read by the instance when the db is getting into the mount mode. Contains information about physical structure of the db. ie. where the redo log files are, db file files are;
To know where your control files are;
SQL> select name from v$controlfile
Control files are most of the time multiplexed
If you have lots of dbfiles, you might want to back them up here.
Talks about how is our data logically organized in the tablespace. i.e structures that can only be queried in the database. The largest logical storage structure is called the TABLESPACE
Used for metadata information. Stores information about the structure of your whole database.
Is used for auxillary purposes. it supports system tablespace
Note: make sure users don't store data in system tablespace. Know that when working with tablespaces, what you are doing is that you are logically arranging your storage structures. You can have as many Tablespaces as you want.
Stores the before image information about your data. e.g performing a rollback
Used for sorting data should in case you dont have enough memory to do the sort.
Note: every single object (table, user, views, index, segment etc) will be contained inside a tablespace (only inside a single tablespace)
Segment is the next smallest logical unit. E.g you can have Person table segment, Emp Table segment or Personnel Index Segment etc.
Types of Segments
Note: You can scatter you segments among different tablespaces depending on how you want to organize your storage structure.
So when you create a table, it will be automatically given a chunk of space called a Segment. Once that space is filled up in that segment, Oracle is going to allocate another space in that area called an EXTENT. Once the extent is filled up, Oracle will create more EXTENT to cater for your storage space.
An extent is therefore defined as several contiguous database blocks.
Note: You can specify a max number of extents if you want to.
Is the smallest logical unit. it doesn't map exactly into an OS block. It is a multiple of the OS block size.