ORA-28534: Heterogeneous Services preprocessing error
Cause: One of the things that the Heterogeneous Services can do is to preprocess parts of SQL statements that contain implicit coercions or calls to explicit coercion functions like TO_CHAR TO_NUMBER or TO_DATE. For example, it could convert a call to TO_DATE to a bind variable, pre-evaluate the TO_DATE function call and pass the resulting value to the non-Oracle system as the bind value. This behavior is controlled by some coercion related capabilities. If the capabilities are set incorrectly, the HS could encounter errors when it attempts to do the preprocessing. If it does then this error will be signaled.
Action: The capability table settings are controlled by the agent vendor and can be modified by the DBA. Contact your DBA and agent vendor and get the correct set of capabilities installed.
ORA-28534是Oracle数据库处理异构数据时显示的一种错误。异构数据是指来自不同系统或不同文件的数据，例如在一个Oracle数据库中，有一个来自SQL-Server的这种类型的数据。
ORA-28534：“ Heterogeneous Services preprocessing错误”意味着发生了异构数据的查询预处理错误。换句话说，当尝试在Heterogeneous Services连接上的Oracle数据库中引用远程数据源中的对象时，可能会发生此错误。
ORA-28534：发生了异构数据查询预处理错误。
1、首先，检查您是否使用了最新的Oracle客户端库。
2、检查您是否已成功安装Hyper文本标记语言（HTML）KB 215187。
3、检查您是否以正确的权限登录到服务器。
4、检查是否在SQL Server中有任何一些功能，由于数据权限或表字段属性等原因，无法从Oracle进行查询。
5、可以重置数据类型，以便您可以继续使用HS，或完全重新配置HS。
6、您还可以尝试使用OracleHSHistry删除查询，以解决可能的无效列名问题。