Master tenant in Hybris
根据help.hybris.com的介绍，每个Hybris server只有1个master tenant，该tenant自动创建且不能删除。
tenant信息在admin console里查看：
所有其他tenant(成为slave tenant)的technical setting，也就是JVM的setting都默认继承自master tenant:
但是和Netweaver一样，Hybris里每个tenant允许定义自己的locale和timezone, currency, date format设置。
System client in Netweaver
SAP help里的介绍:
Special client in AS ABAP with the client ID "000". The system client is where system-specific system programs run. When you log on to the system client of a multitenancy AS ABAP, you are not subject to the restrictions caused by tenant isolation. Furthermore, other clients have read-only access to data stored there under the client ID of the system client.
Client 000 is basically used as working client only when you do support pack upgrade or ABAP load generations (SGEN) and implementing additional languages, etc. Otherwise, client 000 should not be used as a working client.
以前做BYD时，成都开发团队在dev系统上给客户做好addon，然后把package好的content(其实就是一个.zip文件)安装到测试系统上. 安装流程就是首先登陆测试系统的client 000.
原则上system client不允许拿来做transaction处理，所以才有了下面的check:
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来源：https://www.cnblogs.com/sap-jerry/p/12370746.html