因为有个场景，需要用到Oracle 21c的环境中，打算在云主机上安装一个。看了一下官网的安装文件下载，目前提供了三个平台(Linux x86-64、HP-UX ia64和Windows x64)的介质，
https://www.oracle.com/database/technologies/oracle-database-software-downloads.html
Linux平台，官网提供了rpm和home两种安装途径，这点和19c是相同的，因此安装过程，应该是相同的，
我们选择rpm安装，19c的rpm安装CDB和非CDB都做过测试，如下所示，
《非Oracle Linux下Oracle 19c CDB数据库安装》
参照19c的安装过程，尝试安装21c。
1. 安装preinstall
rpm安装的前奏，是通过安装preinstall来给环境做一些准备，如下是针对Oracle Linux 7和Oracle Linux 8的preinstall包下载地址，
虽然此处说的都是针对Oracle Linux，但实际我这次安装的环境是CentOS 7.9，Linux内核的同样适用。
preinstall其实就是装了一些安装过程中需要的依赖包，之前版本中我们都是手工做的准备，从19c开始，集成到了preinstall中，便于自动化安装，降低安装难度，如果安装过程中提示少了一些辅助包，就得自行安装，
[root@VM-20-15-centos software]# rpm -ivh oracle-database-preinstall-21c-1.0-1.el7.x86_64.rpm
warning: oracle-database-preinstall-21c-1.0-1.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
error: Failed dependencies:
ksh is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
nfs-utils is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
policycoreutils-python is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
smartmontools is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
sysstat is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
xorg-x11-utils is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64
xorg-x11-xauth is needed by oracle-database-preinstall-21c-1.0-1.el7.x86_64安装这些缺少的依赖包，再次执行，
[root@VM-20-15-centos software]# rpm -ivh oracle-database-preinstall-21c-1.0-1.el7.x86_64.rpm
warning: oracle-database-preinstall-21c-1.0-1.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
package oracle-database-preinstall-21c-1.0-1.el7.x86_64 is already installed2. 安装21c数据库软件
CentOS 7.9用oracle-database-ee-21c-1.0-1.ol7.x86_64.rpm来安装。rpm安装Oracle默认的路径是/opt/oracle，安装前需要确认该路径的权限是oracle可用的，如果是root，执行安装时，就会提示错误，
[root@bisal software]# rpm -ivh oracle-database-ee-19c-1.0-1.x86_64.rpm
warning: oracle-database-ee-19c-1.0-1.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
[SEVERE] The install cannot proceed because ORACLE_BASE directory (/opt/oracle)
is not owned by "oracle" user. You must change the ownership of ORACLE_BASE
directory to "oracle" user and retry the installation.
error: %pre(oracle-database-ee-19c-1.0-1.x86_64) scriptlet failed, exit status 1
error: oracle-database-ee-19c-1.0-1.x86_64: install failed此时要改下权限，
chown -R oracle:oinstall /opt/oracle再次执行，就会正常安装，
[root@VM-20-15-centos software]# rpm -ivh oracle-database-ee-21c-1.0-1.ol7.x86_64.rpm
warning: oracle-database-ee-21c-1.0-1.ol7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:oracle-database-ee-21c-1.0-1 ################################# [100%]
[INFO] Executing post installation scripts...
[INFO] Oracle home installed successfully and ready to be configured.
To configure a sample Oracle Database you can execute the following service configuration script as root: /etc/init.d/oracledb_ORCLCDB-21c configure此处碰到了坑，正常情况下，安装软件，/opt/oracle中应该至少包括这些文件夹，如果不是这些，很可能是有问题，关注控制台活着日志中有无错误，
cd /opt/oracle
drwxr-x--- 3 oracle oinstall 4096 Jul 1 23:50 cfgtoollogs
drwxr-x--- 2 oracle oinstall 4096 Jul 1 23:50 dbs
drwxrwxr-x 23 oracle oinstall 4096 Jul 1 23:50 diag
drwxr-x--- 3 oracle oinstall 4096 Jul 1 23:50 homes
drwxrwx--- 4 oracle oinstall 4096 Jul 1 23:50 oraInventory
drwxr-xr-x 3 oracle oinstall 4096 Jul 1 23:46 product另外，可能由于我的路径权限问题，提示我很多文件权限错误，
[root@VM-20-15-centos init.d]# /etc/init.d/oracledb_BISALCDB_21c configure
Configuring Oracle Database BISALCDB.
[FATAL] [DBT-10011] Incorrect ownership/permissions detected for the file (/opt/oracle/product/21c/dbhome_1/bin/oradism).
CAUSE: Following nodes does not have required file ownership/permissions: Node :vm-20-15-centos
PRVG-11960 : Set user ID bit is not set for file "/opt/oracle/product/21c/dbhome_1/bin/oradism" on node "vm-20-15-centos".
PRVG-2031 : Owner of file "/opt/oracle/product/21c/dbhome_1/bin/oradism" did not match the expected value on node "vm-20-15-centos". [Expected = "root(0)" ; Found = "oracle(54321)"]
ACTION: Run the Oracle Home root script as the "root" user to fix the permissions.
[FATAL] [DBT-05509] Failed to connect to the specified database (BISALCDB).
CAUSE: OS Authentication might be disabled for this database (BISALCDB).
ACTION: Specify a valid sysdba user name and password to connect to the database.
Database configuration failed.例如$ORACLE_HOME/bin中这个文件应该是个链接文件，
[root@VM-20-15-centos bin]# ll oradism
-rwsr-x--- 1 root oinstall 1867552 Jul 28 2021 oradism但是我安装的环境中该文件是个文件，
[root@VM-20-15-centos bin]# ll oradism
-rwxr-x--- 1 root oinstall 1867552 Jul 28 2021 oradism此时再通过chown调整文件夹时，可能还是有问题，一定要在执行configure前就调整好/opt/oracle的权限。
3. 安装21c数据库
和19c相同，21c可以通过配置oracledb_$ORACLE_SID_21c这个文件来安装数据库，
P.S. 如果改了原始的oracledb_ORCLCDB_21c名称为
oracledb_BISALCDB_21c，
则/etc/sysconfig的oracledb_ORCLCDB-21c.conf要改为
oracledb_BISALCDB-21c.conf，
[root@VM-20-15-centos init.d]# ./oracledb_BISALCDB_21c configure
Configuring Oracle Database BISALCDB.
Prepare for db operation
8% complete
Copying database files
31% complete
100% complete
[FATAL]
Parsing command line arguments:
Parameter "silent" = true
Parameter "local" = true
Parameter "inscomp" = server
Parameter "insprtcl" = TCP
Parameter "orahome" = /opt/oracle/product/21c/dbhome_1
Parameter "instype" = custom
Parameter "listener" = LISTENER
Parameter "lisport" = 1521
Parameter "cfg" = local
Parameter "responsefile" = /opt/oracle/product/21c/dbhome_1/network/install/netca_typ.rsp
Done parsing command line arguments.
Oracle Net Services Configuration:
LISTENER:No valid IP Address returned for the host VM-20-15-centos.
Profile configuration complete.
Check the trace file for details: /opt/oracle/cfgtoollogs/netca/trace_OraDBHome21cEE-22070212AM1239.log
Oracle Net Services configuration failed. The exit code is 1
8% complete
0% complete
Look at the log file "/opt/oracle/cfgtoollogs/dbca/BISALCDB/BISALCDB.log" for further details.
Database configuration failed.此处报错了，看下提示，说的是配置Listener时，找不到主机名对应的有效IP地址，从netca日志，可以再次确认，
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1330] InetAddress.getByName(127.0.0.1): /127.0.0.1
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1332] Local host IP address: VM-20-15-centos/127.0.0.1
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1334] Local host name: VM-20-15-centos
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1345] Address VM-20-15-centos
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1345] Address VM-20-15-centos
[main] [ 2022-07-02 00:12:40.913 CST ] [ConfigureListener.isPortFree:1407] No IP address returned for host. VM-20-15-centos
[main] [ 2022-07-02 00:12:40.913 CST ] [SilentConfigure.silentConfigureListener:398] oracle.net.ca.IllegalEndpointException: No valid IP Address returned for the host VM-20-15-centos.这种情况下，需要配置/etc/hosts，增加主机名和当前内网IP的关系，
vi /etc/hosts
x.x.x.x VM-20-15-centos重新安装，就可以正常执行，
[root@VM-20-15-centos init.d]# ./oracledb_BISALCDB_21c configure
Configuring Oracle Database BISALCDB.
Prepare for db operation
8% complete
Copying database files
31% complete
Creating and starting Oracle instance
32% complete
36% complete
40% complete
43% complete
46% complete
Completing Database Creation
51% complete
54% complete
Creating Pluggable Databases
58% complete
77% complete
Executing Post Configuration Actions
100% complete
Database creation complete. For details check the logfiles at:
/opt/oracle/cfgtoollogs/dbca/BISALCDB.
Database Information:
Global Database Name:BISALCDB
System Identifier(SID):BISALCDB
Look at the log file "/opt/oracle/cfgtoollogs/dbca/BISALCDB/BISALCDB0.log" for further details.
Database configuration completed successfully. The passwords were auto generated, you must change them by connecting to the database using 'sqlplus / as sysdba' as the oracle user.4. 连接数据库
数据库安装完成，可以登录了，因为21c不支持非CDB，所以sqlplus / as sysdba登录的就是CDB，我们安装时配置了一个PDB，可以通过alter session set container或者tns等方式登录到这个PDB，
此处又碰到了一个坑，我在$ORACLE_HOME/network/admin的tnsnames.ora中配置了，
BISALPDB = (DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = VM-20-15-centos)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = BISALPDB1)
)
)正常来讲，sqlplus user/password@bisalpdb就可以登陆，但是一直提示，
ORA-12514的错误就是TNS配置有误，但看了下文件，确实没什么错误。经过多次尝试，即使我删除了$ORACLE_HOME/network/admin/
tnsnames.ora的内容，都能执行tnsping BISALCDB，这就奇怪了。
"事出反常必有妖"，对比了多次配置文件、监听配置等信息，发现一个疑点，lsnrctl status中的Listener Parameter File的路径是/opt/oracle/homes/，并不是/opt/oracle/product/...，
再看下/opt/oracle/homs/的tnsnames配置文件，确实只存在上述测试的BISALCDB，难怪删了/opt/oracle/product的tnsnames.ora内容，并未生效，原来改错了文件，但是为什么此处监听参数文件是这个，不太能考究了，很可能是初次安装的时候，配置有些问题，某个参数采用了默认的，
[oracle@VM-20-15-centos admin]$ cat tnsnames.ora
# tnsnames.ora Network Configuration File: /opt/oracle/homes/OraDBHome21cEE/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
LISTENER_BISALCDB =
(ADDRESS = (PROTOCOL = TCP)(HOST = VM-20-15-centos)(PORT = 1521))
BISALCDB =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = VM-20-15-centos)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = BISALCDB)
)
)为了解决这个，我是删除了/opt/oracle/homes错误路径的tnsnames.ora、listener.ora，重启监听，就会找$ORACLE_HOME/network/admin的tnsnames.ora，
如果哪位朋友知道更准确地改Listener Parameter File值的方式，还请指教。
此时就可以用TNS正常登录到PDB，
21c的整体使用操作上，和19c相差不太大，新特性的方面，还需要测试了解。
