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Changing dynamic SGA and PGA components

As we have noted, Oracle provides alter system commands to allow the DBA to change the configuration of the Oracle RAM memory. Before we look at using these features for automatic tuning, let’s briefly review the main parameters and see how they operate. The output below is an example of a change which has been rejected by Oracle because there is insufficient UNIX memory to expand the selected pool

SQL> alter system set shared_pool_size=64m;
alter system set shared_pool_size=64m
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-04033: Insufficient memory to grow pool

In the case of the above example, the error was generated because the command would have exceeded the value of sga_max_size parameter. In the example below, we expand the shared pool to 300 megabytes, and se can immediately confirm the change with the show parameters command.

SQL> connect system/manager as sysdba;
SQL> alter system set shared_pool_size=300m;

System altered.

SQL> show parameter shared_pool

------------------------------------ ----------- -----------
shared_pool_reserved_size big integer 1258291
shared_pool_size big integer 33554432

The above is an excerpt from the "Oracle UNIX Administration Handbook" by Oracle press, authored by Donald K. Burleson.


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