Modifying Memory Settings – Automatic PGA Memory Management

Modifying memory settings for automatic Program Global Area (PGA) memory management involves using the PGA Advisor graph in Oracle Enterprise Manager Database Express (EM Express) to modify the instance PGA size. This section assumes that automatic memory management is disabled, and that automatic PGA memory management is enabled.

Note:

When you disable automatic memory management, automatic PGA memory management remains enabled by default.

To modify the instance PGA size:

  1. In EM Express, from the Configuration menu, select Memory.

    The Memory Management page appears. If the database has either automatic shared memory management or manual shared memory management enabled, then the PGA Advisor Graph appears as the second chart to the right of the Memory Settings section.

  2. Use the PGA Advisor graph to predict the estimated cache hit percentage for potential database cache sizes.

    In the PGA Advisor graph:

    • Potential values for the PGA_AGGREGATE_TARGET initialization parameter are represented on the horizontal axis of the graph. The unit size (for example, MB or GB) is also indicated on the horizontal axis. The current setting of the PGA_AGGREGATE_TARGET initialization parameter is indicated by a blue dot.

    • The corresponding estimated cache hit percentage values are represented on the vertical axis of the graph. The plotted values are expressed as a percentage relative to the current setting of the PGA_AGGREGATE_TARGET initialization parameter.

    An orange line on the graph plots different values that can be specified for the PGA_AGGREGATE_TARGET initialization parameter. Click any dot on the orange line to see an estimate of the percentage of cache hits for the PGA_AGGREGATE_TARGET value represented by that dot.

    In this figure, the PGA Advisor graph indicates that increasing the current value of the PGA_AGGREGATE_TARGET initialization parameter will not increase the percentage of cache hit.

  3. To change the value of the PGA_AGGREGATE_TARGET initialization parameter:

    1. Click Configure Memory on the Memory Management page.

      The Initialization Parameters page appears.

    2. Select the PGA_AGGREGATE_TARGET initialization parameter and click Set.

      The Set Initialization Parameter page appears.

    3. In the Scope field, enter the scope for this change.

      See "Viewing and Modifying Initialization Parameters" for more information about specifying a scope of Memory, or SPFile, or both.

    4. In the Value field, enter the new value for the PGA_AGGREGATE_TARGET initialization parameter.

    5. Click OK.

      A confirmation message appears.

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