ORA-12154 generally indicates a problem with your Oracle Net configuration files (files tnsnames.ora and sqlnet.ora) or your LDAP server if you are using that in lieu of Oracle Net.
Generally, start with file $ORACLE_HOME/rdbms/admin/sqlnet.ora. This file has the line SQLNET.DIRECTORY_PATH. If this is set to TNSNAMES then you are using Local Naming and you need to ensure certain things are set corredtly in files sqlnet.ora and tnsnames.ora. All of the below tips assume you are using Local Naming.
Next, in the same file sqlnet.ora, look at the parameter NAMES.DEFAULT_DOMAIN. Write down the value. When Oracle created the file it probably put your network domain name, which most people don't want. Again, just make a note at this point.
Next, edit file tnsnames.ora and you should see an entry that starts with the format SID.DOMAIN = .... When you try to connect to a database named ORCL, for example, the value of DEFAULT_DOMAIN is appended to the database name. If the value of NAMES.DEAFAULT_DOMAIN = ACME.COM, then your tnsnames.ora file needs a block that starts ORCL.ACME.COM = ....
Therefore, all you may need to do is edit file tnsnames.ora to ensure each block starts with the correct SID.DOMAIN.
Note: the domain mentioned above has nothing to do with your database init.ora parameter DB_DOMAIN. That is used in the CONNECT_DATA clause of the tnsnames entries, but not in the alias part of the entry (line 1 of each block in tnsnames.ora is called the "alias".)