Both variables improve INSERT performance into MDC tables:

DB2_TRUST_MDC_BLOCK_FULL_HINT speeds up the search for a block containing free space for large MDC cells. It was added after we experienced a performance degradation when loading very large InfoPackages into PSA (resulting in very large MDC cells because MDC is defined on REQUEST).

DB2_MDC_MAX_CACHE_SIZE improves performance when inserting unsorted data into many MDC cells.