@Override
  public void validatePoolFactory(PoolFactory poolFactory) {
    // If the specified pool factory is null, by definition there is no pool factory to validate.
    if (poolFactory != null && !Objects.equals(this.poolFactory, poolFactory)) {
      throw new IllegalStateException("Existing cache's default pool was not compatible");
    }
  }
Set the default pool on a new GemFireCache.
geode-core/src/main/java/org/apache/geode/internal/cache/GemFireCacheImpl.java