Tuesday, September 06, 2005

refreshing my memory

Hi friends,

I get interview call and I am just refreshing my memory after going through with my manuals which I get from performance tuning training from Oracle Education centre.

So get some good point and here I want to share with you.

Why we need to check alter log file regularly.
•To detect internal errors (ora-600)
•Block corruption errors (ora-1578 or ora-1498)
•Operation that effect database structures and parameters, statement such as CREATE
•View nondefualt initialization parameter
•Checkpoint start and end times
•Incomplete checkpoints
•Time to perform archiving
•Instance recovery start and complete times
•Dead lock and timeout errors.

Difference between V$view and X$tables.
V$ views
•These are based on X$tables, therefore some V$ views are available in NOMOUNT and
MOUNT stages.
•They are listed in v$fixed_table.
•The V$ views actually synonyms for V_$ views and they are belong to the sys user.

X$ tables
•These are not usually queried directly, not all the information is necessarily
•The X$ tables are memory structures that hold instance information and are available
when the instance is in NOMOUNT and MOUNT state.
•The X$ tables are dynamic and there contents are constantly changing.

The V$ views and the underlying X$ tables are populated at instance startup and cleared at shutdown.

When SYSTEM tablespace is locally managed
•It is not possible to create dictionary managed tablespaces.
•It is not possible to migrate locally managed tablespace to dictionary managed.
•It is not possible to transport dictionary managed tablespace into database with
locally managed system tablespace. Note that after the transport, dictionary managed
tablespaces cannot be made read/write. The tablespace can be migrated to locally
managed and then read/write.
•It is possible to DROP and READ ONLY dictionary managed tablespace when system
tablespace locally managed.

Note : If the database create using DBCA then locally managed system tablespace is the default.

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