We are planning to Migrate our Oracle 11g database to Google Cloud spanner, and I want to confirm that it is possible or not. We need to plan migration steps, what are the risks and possible troubles during migration. Need opinion from experts regarding said migration, I have done much googling but still need recommendations for migration to cloud spanner.
Anything is possible if you have enough resources and time!
The relative complexity depends on your application, notably how much of your Oracle DB's features you are using, because Cloud Spanner is not feature-equivalent to Oracle (or for that matter to many other DB's).
If you are using it as a simple transactional datastore, then it would be relatively easy. If you have triggers, stored procedures, queues, per-user/per-table ACLs, on-delete clauses then you are going to have a lot of extra work.
To have an idea of the work involved, you can watch at a Cloud Next #18 talk where migration to Cloud Spanner from both RDBMS and NoSQL DBs are discussed in general terms.