To enable the Global Meta Cache feature, the pgx_global_metacache parameter must specify an upper limit on the size of the shared memory (Hereinafter, the GMC area) dedicated to Global Meta Cahche. Ideally, this upper limit should be the size estimated in “Appendix A Parameters”. Values lower than this can still work, but refer to "14.1.3 How the GMC Memory Area Is Used" on using the GMC area to understand the disadvantages.