Oracle客户端与Oracle数据库之间是有兼容支持关系的，有些低版本的Oracle Client连接到高版本的数据库是不支持的，其实Oracle官方文档 Client / Server Interoperability Support Matrix for Different Oracle Versions (Doc ID 207303.1)[1]中有详细的介绍，如果你要升级数据库的话或遇到客户端与数据库兼容问题的话，建议仔细查看此文档。下面图片是文中的兼容矩阵关系图。
Specific Notes:
#1 - See Note 207319.1
#2 - An ORA-3134 error is incorrectly reported if a 10g client tries to connect to an 8.1.7.3 or lower server. See Note 3437884.8 .
#3 - An ORA-3134 error is correctly reported when attempting to connect to this version.
#4 - There are problems connecting from a 10g client to 8i/9i where one is EBCDIC based. See Note 3564573.8
#5 - For connections between 10.2 (or higher) and 9.2 the 9.2 end MUST be at 9.2.0.4 or higher. Connections between 10.2 (or higher) and 9.2.0.1, 9.2.0.2 or 9.2.0.3 have never been supported.
#6 - For connections between 11.1 (or higher) database server and 10.1 / 10.2 database server across a database link the 10g end MUST be at 10.1.0.5 / 10.2.0.2 (or higher) respectively in order to use PLSQL between those versions. (This does not apply to normal 11g clients to 10g database server only server to server and a few very specific client products, such as Oracle Forms). See Note 4511371.8 for more details.
#7 - For database link connections between 11.1 (or higher) and 10.2 the 10g end MUST be at 10.2.0.2 (or higher) in order to use PLSQL between those versions. See Note 4511371.8 for more details.
#8 - Attempting to connect from 9.2 to 12.1 will fail with an "ORA-28040: No matching authentication protocol" error.
#9 - 11.2.0.3 or 11.2.0.4 only. For Oracle Autonomous Transaction Processing and Oracle Autonomous Data Warehouse, there is additional limitation and 11.2.0.4 is the minimum supported client version.
#10 - For the IBM z/OS platform only, Oracle will continue to test past 2014, at its discretion, new versions of the database running on non-z/OS platforms with the older 10.2 client running on z/OS. For more information, please refer to Note 461234.1 - Oracle Database on z/OS Support Status.
#11 - 32-bit DB23c client is not available on any platform. However, you can use older 32-bit clients (e.g. 19c) with DB23c server based on this matrix unless the platform desupport notice indicates otherwise.
#12 - 12.1.0.2 only. For 11.2 interoperability, 11.2.0.4 is requir
下图是完整的矩阵兼容关系图（FULL INTEROPERABILITY SUPPORT MATRIX）
参考资料
[1]1: https://support.oracle.com/epmos/faces/DocumentDisplay?_afrLoop=459942577177294&id=207303.1&_afrWindowMode=0&_adf.ctrl-state=yivmtoe98_572