Use of Embeded search in ESS/MSS

Hi Experts,

We have implemented ESS and MSS WDA in ECC 6.0 EHP6 and we are accessing ESS/MSS from Portal 7.31.

For Talent profile in MSS, We have also activated Talent Management business functions ERP_ENTERPRISESEARCH, HCM_TMC_CI_1, HCM_TMC_CI_2 & HCM_TMC_CI_3 in ECC.

Talent profile is working fine in ESS/MSS without TREX .

Could you please tell me the system perspective requirement for TREX?

Do I really need to install trex if I activate the business function ERP_ENTERPRISESEARCH?

Regards,

Sridharan R.