Depends on the cause for this.
I'd start by checking for shared SQL cache evictions and see if the shared SQL cache is appropriately sized.
Check Martin Frauendorfer's script collection for that (SAP note #1969700) as well as SAP notes
| 2000002 * | FAQ: SAP HANA SQL Optimization |
| 2040002 | Size recommendation for the HANA SQL Plan Cache |