The SID prefix is the first 8 characters of the database name, but it can only contain the characters a-z, A-Z, and 0-9. Special characters are omitted.
For a RAC database, the instance number format is generated differently for a policy-managed instance than for an admin-managed instance.
For policy-managed database instances, the format is name_# where name is the SID prefix. For admin-managed database instances, the format is name# where name is the SID prefix.
Using the following example of a global database named “evanracprod.example.com”, the SID prefix would be evanracp1 for the first instance of a derived admin-managed database, and evanracp_1 for the first derived instance name for policy managed instance.
Have a RAC instance you want to check the managed instance type on? Try this:
[oracle@rac1 ~]$ srvctl config database -d cdbrac1
Database unique name: cdbrac1
Database name: cdbrac1
Oracle home: /u01/app/oracle/product/12.2.0.1/db_1
Oracle user: oracle
Spfile: +DATA/CDBRAC1/PARAMETERFILE/spfile.298.947356499
Password file: +DATA/CDBRAC1/PASSWORD/pwdcdbrac1.282.947356141
Domain: localdomain
Start options: open
Stop options: immediate
Database role: PRIMARY
Management policy: AUTOMATIC
Server pools:
Disk Groups: DATA
Mount point paths:
Services:
Type: RAC
Start concurrency:
Stop concurrency:
OSDBA group: dba
OSOPER group: dba
Database instances: cdbrac11,cdbrac12
Configured nodes: rac1,rac2
CSS critical: no
CPU count: 0
Memory target: 0
Maximum memory: 0
Default network number for database services:
Database is administrator managed
[oracle@rac1 ~]$