Oracle 11g

to see the version - SELECT * PRODUCT_COMPONENT_VERSION;

Shared Pool

1. Library cache - Every time you execute a statement, the information is stored in the library cache. That way, the next time you execute the statement not much has to
occur.
2. Dictionary cache - The dictionary cache is also frequently used for parsing when you execute
SQL.
3.The quickest result cache - This lets Oracle skip the execution part of the, er, execution, for lack of a better term, and go directly to the result set, if it exists.
4. Least Recently Used algorithm - If the library cache is short on space, objects are thrown out. Statements that are used the most stay in the library cache the longest.

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When you install 10g express you have to do the following:


Why I got ORA-27121: unable to determine size of
shared memory segment ?

A. The full erros stack:
ERROR:
ORA-01034: ORACLE not available
ORA-27121: unable to determine size of shared memory
segment
Linux Error: 13: Permission denied

This is caused by Oracle installer not setting setuid
on $ORACLE_HOME/bin/oracle.

To fix do:
$ cd $ORACLE_HOME/bin
$ chmod 6751 oracle


$ORACLE_HOME should be this, /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/