服务器发生错误时所提供的唯一错误码，打印在 Proxy 后端或 JDBC 启动日志中。

    错误码错误信息
    SPI-00001No implementation class load from SPI %s with type %s.
    DATA-SOURCE-00001Data source unavailable.
    PROPS-00001Value %s of %s cannot convert to type %s.
    PROXY-00001Load database server info failed.
    SPRING-00001Can not find JNDI data source.
    SPRING-SHARDING-00001Can not support type %s.