The purpose of this memory segment is to reduce the load on the Shared Pool. The Large Pool is used in several operations, including the following:

1. RMAN: When the RMAN Channel Processes are activated, the Large Pool is used for caching buffers during backup and recovery operations.
2. Shared Server Processes: If the Shared Server is configured, the Session UGAs (User Global Areas) are stored in the Large Pool.
3. Parallel Execution Servers: When Parallel Query or DML (Data Manipulation Language) operations are enabled, the Parallel Servers will connect via the Large Pool.

In general, if the Large Pool is not created, the instance will still work, but it may not function optimally.

The size of the Large Pool is controlled by the LARGE_POOL_SIZE parameter.

You can monitor the Large Pool using the view V$SGASTAT.

If the LARGE_POOL_SIZE parameter is not explicitly configured, the default size will depend on other parameters. For example, if Parallelism is enabled, the Large Pool will automatically be created.