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Real storage management mode

The Advisor Selection List indicates the storage management mode under which Pool Advisor operates. The Real Storage Advisor determines the operating mode based on the available real storage in the DBM1 address space and on the LPAR.

Ideally, when an individual Pool Advisor sends a recommendation to the System Advisor, the recommendation is added to the Pending Action List, from where it can be run. However, the ability to recommendations depends on the availability of storage resources. The Real Storage Advisor monitors available resources and sets the operating mode that suits the storage constraint conditions in effect. If those conditions change, the operating mode is changed to match the new conditions.

Real storage management is enabled when the PGFIX initialization parameter is set to Y (Yes).

Related topics

Parameter-variables-and-rules

Storage management mode


Warning

Important

The default PGFIX value for Pool Advisor is N (No).


Real storage management mode values

The real storage management mode can take the following values:

  • NORMAL mode indicates that recommendations to page fix buffer pools will be provided as good candidates are identified. NORMAL mode takes effect when all of the following conditions are true:

    • The real storage used by buffer pools is below the WARNING threshold.
    • The amount of real storage used by the Db2 subsystem is below the WARNING threshold calculated using the RSTGMAX_LPAR_PERCENT initialization parameter.
    • The amount of real storage available to the Db2 subsystem is above the WARNING threshold defined in the RSTAVAIL_WARN initialization parameter.
    • The amount of real storage available on the LPAR is greater than the calculated WARNING threshold.
    Warning

    Important

    Buffer Pool Advisor recommends PGFIX(YES) conditionally.

  • PAGEABLE mode indicates that no recommendations for page fixing buffer pools will be offered in this state. PAGEABLE mode takes effect when any of the following conditions is true:

    • The real storage used by buffer pools has reached the WARNING threshold, but less than the ALERT threshold.
    • The amount of real storage used by the Db2 subsystem has reached the WARNING threshold, but less than the ALERT threshold calculated using the RSTGMAX_LPAR_PERCENT initialization parameter.
    • The amount of real storage available to the Db2 subsystem is greater than the ALERT threshold defined in the RSTAVAIL_ALERT initialization parameter, but less than or equal to the WARNING level threshold defined in the RSTAVAIL_WARN initialization parameter.
    • The amount of real storage available on the LPAR is greater than the calculated ALERT threshold but less than or equal to the calculated WARNING threshold.
    Warning

    Important

    Buffer Pool Advisor recommends PGFIX(NO) only. This mode is triggered at the Real Storage Advisor WARNING level.

  • DECREASE mode indicates that real storage constraints exist to the extent that only recommendations to convert from page fixed to pageable. DECREASE mode takes effect when any of the following conditions is true:

    • The real storage used by buffer pools has reached the ALERT threshold.
    • The amount of real storage used by the Db2 subsystem has reached the ALERT threshold calculated using the RSTGMAX_LPAR_PERCENT initialization parameter.
    • The amount of real storage available to the Db2 subsystem is less than or equal to the ALERT threshold defined in the RSTAVAIL_ALERT initialization parameter.
    • The amount of real storage available on the LPAR is less than or equal to the calculated ALERT threshold.
    Warning

    Important

    Buffer Pool Advisor recommends PGFIX(NO) and triggers a Virtual Storage Management Mode, DECREASE. As a result:

    • Only the buffer pool decrease size recommendations are added to the pending action list. 
    • The buffer pool increase recommendations are not added to the pending action list.

    This mode is triggered at Real Storage Advisor ALERT level.

 

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BMC AMI Pool Advisor for Db2 13.1