Application Domain Indexes

Application domain index gives the user ability to supply new index technology.Most people will never make use of it his particular API to build a new index type. The inetMedia set of functionally ,implemented  using  the Application Domain indexing feature will  provide indexing on text,XML  documents and image.

Function-based Indexes

A function-based index includes columns that are either transformed by a function, such as the UPPER function, or included in an expression, such as col1 + col2.

Reverse Key index

There is an option to create index entries as reversed, which is called reverse key indexes. Oracle stores the index entries as their bytes reversed.

B tree index

A b-Tree index is a data structure in the form of a tree - no surprises there - but it is a tree of database blocks, not rows. Imagine the leaf blocks of the index as the pages of a phone book.
Each page in the book (leaf block in the index) contains many entries, which consist of a name (indexed column value) and an address (ROWID) that tells you the physical location of the telephone (row in the table).

Mapping Bitmaps to Rowids Efficiently
 

Use SQL statements with the ALTER TABLE syntax to optimize the mapping of bitmaps to rowids. The MINIMIZE RECORDS_PER_BLOCK clause enables this optimization, and the NOMINIMIZE RECORDS_PER_BLOCK clause disables it.

Maintenance Considerations for Bitmap Indexes

Index  Definition

An index  is a performance-tuning method of allowing faster retrieval of records. An index creates an entry for each value that appears in the indexed columns. By default, Oracle creates B-tree indexes.

  SCN can refer to:

    System Change Number - A number, internal to Oracle that is incremented over time as change vectors  
                           are generated, applied, and written to the Redo log.

  While user is issuing DML transaction the  redo entrie for this transaction Is store to the buffer in to SGA. And  after commit issue redo data written to the  redo log file  which physical located on  hard disk. This is normal practice and it is called synchronous Commit.  Oracle does not return control until the transaction physically written.

But this practice not very much acceptable for  high speed Transition.   this point of view oracle introduce Asynchronous commit  in 10g release 2.

PREPARING THE PRIMAY DATABASE

SQL > alter database force logging

1. create a password file.

2. set initialization parameters in primary database.

a.
 db_name = databasename
 db_unique_name = databasename
 log_archive_config = ' DG_CONFIG = (primarydbname,standbydbname)

b.
log_archive_dest_2=
'service = standbydbname
valid for = ( online_logfiles,primary_role)
db_unique_name=standbydbname'

c.