我们在12c之前的版本，添加或修改应用SERVICE_NAME的方式是通过修改数据库参数”SERVICE_NAMES”，但是此参数意在19c版本中废弃，并且再次利用此参数会出现alter session set container=pdb命令失效，无法在sqlplus中切换PDB的影响
官方文档提示：
Note:The SERVICE_NAMES initialization parameter is deprecated in Oracle Database 19c and may be desupported in a future release.
Use of the SERVICE_NAMES parameter is no longer actively supported. It must not be used for high availability (HA) deployments and it is not supported for HA operations. This restriction includes FAN, load balancing, FAILOVER_TYPE, FAILOVER_RESTORE, SESSION_STATE_CONSISTENCY, and any other uses.
To manage your services, Oracle recommends that you instead use the SRVCTL command-line utility, the GDSCTL command-line utility, or the DBMS_SERVICE PL/SQL package.实验测试过程：
SQL> select name,open_mode,database_role from v$database;
NAME OPEN_MODE DATABASE_ROLE
------------------ ---------------------------------------- --------------------------------
ALBERTCDB READ WRITE PRIMARY
SQL> show parameter service
NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
service_names string ALBERTCDB
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 PDB9A READ WRITE NO
4 PDB113A READ WRITE NO
SQL>
监听注册SERVICE情况，pdb9a与pdb113a默认serivce已注册并且可以正常对外提供服务：
Service "+ASM" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_ARC" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_DATA" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_MGMT" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_OCR" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_REDO" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_VOTE" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "c36f7bedb52420e5e053d06c050a5e9a" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "c3d979c76e1b0f6de053d06c050a6730" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB" has 2 instance(s).
Instance "ALBERTCDB2", status UNKNOWN, has 1 handler(s) for this service...
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDBXDB" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB_CFG" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB_dgmgrl" has 1 instance(s).
Instance "ALBERTCDB2", status UNKNOWN, has 1 handler(s) for this service...
Service "pdb113a" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "pdb9a" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
The command completed successfully
正常切换PDB：
SQL> alter session set container=PDB9A;
Session altered.
SQL> alter session set container=PDB113A;
Session altered.
修改SERVICE_NAMES参数，添加ALBERT的应用SERVICE:
SQL> show parameter service
NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
service_names string ALBERTCDB
SQL> alter system set service_names='ALBERTCDB,albert';
System altered.
SQL>
SQL>
SQL> show parameter service
NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
service_names string ALBERTCDB,albert
修改完毕后，可以看到监听中PDB默认的SERVICE已经不见了：
Services Summary...
Service "+ASM" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_ARC" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_DATA" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_MGMT" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_OCR" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_REDO" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "+ASM_DG_VOTE" has 1 instance(s).
Instance "+ASM2", status READY, has 1 handler(s) for this service...
Service "albert" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB" has 2 instance(s).
Instance "ALBERTCDB2", status UNKNOWN, has 1 handler(s) for this service...
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDBXDB" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB_CFG" has 1 instance(s).
Instance "ALBERTCDB2", status READY, has 1 handler(s) for this service...
Service "ALBERTCDB_dgmgrl" has 1 instance(s).
Instance "ALBERTCDB2", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
并且CDB中是无法切换PDB的：
SQL> alter session set container=PDB9A;
ERROR:
ORA-44787: Service cannot be switched into.
SQL> alter session set container=PDB113A;
ERROR:
ORA-44787: Service cannot be switched into.
修复方式为：
将SERVICE_NAMES中将SERVICE取出，并且重启CDB
此时需要重启CDB
SQL>
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 1.3100E+11 bytes
Fixed Size 23312360 bytes
Variable Size 3.3286E+10 bytes
Database Buffers 9.7442E+10 bytes
Redo Buffers 245121024 bytes
Database mounted.
Database opened.
SQL> alter session set container=PDB9A;
Session altered.
SQL> alter session set container=PDB113A;
Session altered.