ORA-26724: only SYS is allowed to set the Capture or Apply user to SYS.
Cause: The Capture or Apply user was specified as SYS by a user other than SYS.
Action: Set SYS as the Capture or Apply user while logged in as SYS.
ORA-26724: Only SYS is allowed to set the Capture or Apply user to SYS的含义是，只有SYS用户可以将捕获或应用用户设置为SYS。
该错误通常会在使用Data Guard时出现，此时当用户尝试设置Capture或Apply用户为sys，而当前用户非sys时可能会引发该错误。
要正确处理该错误，请确保您具有sys帐户，然后使用sys帐户尝试使用Data Guard功能。如果您尝试使用sys帐户设置Capture或Apply用户，则可以避免ORA-26724错误。