First check, whether your CPU supports trace - refer to the topic Trace is not licensed.
Trace Buffer is configured in Hardware | CPU Options | SoC.
The option Use all available memory for trace buffer should work in most cases assuming that complete TCM memory is available for Trace.
When a limited amount of TCM memory or Tiles are available for Trace (the rest is used for Calibration):
When whole TCM memory is used for Calibration and the Emulation Device provides optional XTM memory, which is available for trace:
Trace data is stored in the so-called Emulation Memory (EMEM). By default, Emulation Memory consists of a regular memory array (TCM – Trace Calibration Memory) built out of RAM Blocks (Tiles), which can be split into a Trace memory and a Calibration memory part. Additionally, certain Emulation Devices (ED) offer the optional memory XTM (Extended Trace Memory) for Trace. XTM can also be assigned to Calibration. If the Emulation Device with AGBT has TCM or XTM assigned to Trace, TCM Tile0 or XTM Tile0 acts as an AGBT Trace buffer.