add direct memory usage note

Author: xx789633

website/docs/streaming-lakehouse/integrate-data-lakes/lance.md

@@ -72,6 +72,8 @@ Additionally, when following the [Start Datalake Tiering Service](maintenance/ti
 
 > **NOTE**: Fluss v0.8 only supports tiering log tables to Lance.
 
+> **NOTE**: The Lance connector leverages the Arrow Java library, which operates on direct memory. So ensure sufficient off-heap memory for the Flink Task Manager by configuring the `taskmanager.memory.task.off-heap.size` parameter in `<FLINK_HOME>/conf/config.yaml`.
+
 Then, the datalake tiering service continuously tiers data from Fluss to Lance. The parameter `table.datalake.freshness` controls the frequency that Fluss writes data to Lance tables. By default, the data freshness is 3 minutes.
 
 You can also specify Lance table properties when creating a datalake-enabled Fluss table by using the `lance.` prefix within the Fluss table properties clause.