In this age of superlatives, nothing but a phenomenal improvement on performance has become a sine quo non for SAP customers evaluating their a HANA journey. Expectations have really been set sky high.
Again superlatively speaking, the biggest roadblock in achieving this performance improvement are the in the nagging Z-programs that does the bread and butter business operations smoothly and successfully in the existing ECC systems. So the most difficult question being faced is that does the current Z-Programs that are executing the needed business critical & supporting operations and which have evolved over years of gradual build on additional functionalities and break-fixes is ready for HANA or not?
It is very normal to find SAP customers with systems older than 10 years having Z-Programs that have been performing business critical tasks but they have never been touched from a performance improvement perspective. General approach is risk averse and deterioration on performance is to addressed through upgrade of hardware rather than redesign of such programs for better performance.
Considerable amount of heavy lifting will be needed to address lack of performance improvement on such Z-Programs once they are in HANA. There are cases of performance deterioration too which would be extreme but happens.
So having a regular performance tuning on all Z-Programs as they evolve over course of business changes even if they are risky and will lead to big testing effort is better be done on timely basis. Business critical and important Z-Programs being performance tuned at ECC itself makes HANA journey smooth. As the saying goes “Greatest Truths are the Simplest” is very apt here.