000-221 Question #155: Real Exam Question with Answer & Explanation

The correct answer is E. sb_min and sb_max. The sb_min and sb_max parameters are the AIX VMM tuning values that set the lower and upper bounds on filesystem cache memory usage.

Question

An administrator needs to limit the size of the filesystem cache. Which tuning parameters need to be adjusted?

Options

Aminfree and maxfree
Bminperm and maxperm
Cminfreemem and maxfreemem
Dminpgahead and maxpgahead
Esb_min and sb_max

Explanation

The sb_min and sb_max parameters are the AIX VMM tuning values that set the lower and upper bounds on filesystem cache memory usage.

Common mistakes.

A. minfree and maxfree set the free memory list thresholds that trigger the page-stealing daemon (lrud) to reclaim pages, not the filesystem cache size boundaries.
B. minperm and maxperm define the percentage range of real memory frames that may hold persistent file-backed pages, but do not impose a direct bounded size limit on the filesystem cache.
C. minfreemem and maxfreemem are not standard AIX VMM tuning parameters associated with controlling filesystem cache size.
D. minpgahead and maxpgahead control the number of pages read ahead during sequential I/O operations and have no effect on the overall size of the filesystem cache.

Concept tested. AIX VMM filesystem cache size tuning with vmo

Reference. https://www.ibm.com/docs/en/aix/7.3?topic=tuning-virtual-memory-manager-vmm-parameters

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