报错内容：
The unit files have no installation config (WantedBy, RequiredBy, Also, Alias
settings in the [Install] section, and DefaultInstance for template units).
This means they are not meant to be enabled using systemctl.
Possible reasons for having this kind of units are:
1) A unit may be statically enabled by being symlinked from another unit's
.wants/ or .requires/ directory.
2) A unit's purpose may be to act as a helper for some other unit which has
a requirement dependency on it.
3) A unit may be started when needed via activation (socket, path, timer,
D-Bus, udev, scripted systemctl call, ...).
4) In case of template units, the unit is meant to be enabled with some
instance name specified.
[#zeyu#]
编辑文件： /usr/lib/systemd/system/rc-local.service
[root@localhost dbhome_1]# vi /usr/lib/systemd/system/rc-local.service
在文件末尾添加：
[Install]
WantedBy=multi-user.target
添加后，全文为：
# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This unit gets pulled automatically into multi-user.target by
# systemd-rc-local-generator if /etc/rc.d/rc.local is executable.
[Unit]
Description=/etc/rc.d/rc.local Compatibility
Documentation=man:systemd-rc-local-generator(8)
ConditionFileIsExecutable=/etc/rc.d/rc.local
After=network.target
[Service]
Type=forking
ExecStart=/etc/rc.d/rc.local start
TimeoutSec=0
RemainAfterExit=yes
GuessMainPID=no
[root@localhost dbhome_1]# vi /usr/lib/systemd/system/rc-local.service
[root@localhost dbhome_1]# systemctl enable rc-local.service
Created symlink /etc/systemd/system/multi-user.target.wants/rc-local.service → /usr/lib/systemd/system/rc-local.service.
[root@localhost dbhome_1]# chmod +x /etc/rc.d/rc.local
[root@localhost dbhome_1]# cat /usr/lib/systemd/system/rc-local.service
# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This unit gets pulled automatically into multi-user.target by
# systemd-rc-local-generator if /etc/rc.d/rc.local is executable.
[Unit]
Description=/etc/rc.d/rc.local Compatibility
Documentation=man:systemd-rc-local-generator(8)
ConditionFileIsExecutable=/etc/rc.d/rc.local
After=network.target
[Service]
Type=forking
ExecStart=/etc/rc.d/rc.local start
TimeoutSec=0
RemainAfterExit=yes
GuessMainPID=no
[Install]
WantedBy=multi-user.target
添加完成后，重新命令即可：
[root@localhost dbhome_1]# systemctl enable rc-local.service
Created symlink /etc/systemd/system/multi-user.target.wants/rc-local.service → /usr/lib/systemd/system/rc-local.service.
[root@localhost dbhome_1]# chmod +x /etc/rc.d/rc.local
[/#zeyu#]
至此，处理完毕。centos 8 安装Oracle 19c出现以上错误，之前安装18c未出现。