Memory Management

Yes.

The advantages over file system files.

I/O will be improved because Oracle is bye-passing the kernnel which writing into disk.

Disk Corruption will be very less.

The Control File is a small binary file necessary for the database to start and operate successfully. Each Control file is associated with only one Oracle database. Before a database is opened, the control file is read to determine if the database is in a valid state to USE.

The Control file is not accessible, the database does not function properly.

By using dictionaray view's called v$rollstat,dba_rollback_segs.

Due to syntax errors.

This can be monitored in DB_data_files.

By correctly fixing optimal size.

create rollback segment roll1tablespace roll1.

When ever changes happend to the database previous change will be there in the rollback segment.

Hit Ratio is the ratio of shared SQL and PL/SQL items found in the Library Cache versus physical storage.It can also be defined in a mathematical expression as 1 - ((physical reads) / (db block gets + consistent reads)).

We should depend on export/import utility for backup/recovery (fully reliable) The tar command cannot be used for physical file backup, instead we can use dd command which is less flexible and has limited recoveries.

When a user updated a particular table (for example 100 rows) the old value will be retained in the roll back segments(Oracle 8) and now it is Undo segment (oracle 9i). If the user issue a rollback command the old value will be taken from the rollback segment(that too if undo_retention parameter set properly in the parameter file).

Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switchover to place of failed disk.

Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.

LGWR process wirtes all change vectors from theredo log buffer to online redo log file sequentially.

Multiplexing Redo log file called Mirroing. ( Keeping multiple copies in different disks)

1. Edit init.ora file set control_files parameter with multiple location

2. shutdown immediate

3. copy control file to multiple locations & confirm from init.ora contol_files parameter

4. start the database.

5. run this query for changes confirmation - select name from v$controlfile;

The System Global Area in a Oracle database is the area in memory to facilitates the transfer of information between users. It holds the most recently requested structural information between users. It holds the most recently requested structural information about the database. The structure is Database buffers, Dictionary cache, Redo Log Buffer and Shared SQL pool (ver 7.0 only) area.

The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.

It is area in memory that is used by a Single Oracle User Process.

The space used transaction entries and a deleted record does not become free immediately after completion due to delayed cleanout.

Trailing nulls and length bytes are not stored. Inserts of, updates to and deletes of rows as well as columns larger than a single datablock, can cause fragmentation and chained row pieces.

Full back - Complete database

Incremental - Only affected tables from last incremental date/full backup date.

Cumulative backup - Only affected table from the last cumulative date/full backup date.