Comparing database 12cR1 release 126.96.36.199 to 12cR2 release 188.8.131.52.3, I see these new parameters:
adg_imc_enabled TRUE Enable IMC support on ADG allow_global_dblinks FALSE LDAP lookup for DBLINKS allow_group_access_to_sga FALSE Allow read access for SGA to users of Oracle owner group approx_for_aggregation FALSE Replace exact aggregation with approximate aggregation approx_for_count_distinct FALSE Replace count distinct with approx_count_distinct approx_for_percentile none Replace percentile_* with approx_percentile asm_io_processes 0 number of I/O processes per domain in the ASM IOSERVER instance cdb_cluster FALSE if TRUE startup in CDB Cluster mode cdb_cluster_name cfcdba1 CDB Cluster name clonedb_dir CloneDB Directory containers_parallel_degree 65535 Parallel degree for a CONTAINERS() query cursor_invalidation IMMEDIATE default for DDL cursor invalidation semantics data_guard_sync_latency 0 Data Guard SYNC latency data_transfer_cache_size 0 Size of data transfer cache default_sharing metadata Default sharing clause disable_pdb_feature 0 Disable features enable_dnfs_dispatcher FALSE Enable DNFS Dispatcher enable_pdb_isolation FALSE Enables Pluggable Database isolation inside a CDB enabled_PDBs_on_standby * List of Enabled PDB patterns encrypt_new_tablespaces ALWAYS whether to encrypt newly created tablespaces external_keystore_credential_location +DATA/wallets/tde/us external keystore credential location inmemory_expressions_capture DISABLE Controls detection of frequently used costly expressions inmemory_expressions_usage ENABLE Controls which In-Memory Expressions are populated in-memory inmemory_virtual_columns ENABLE Controls which user-defined virtual columns are stored in-memory instance_abort_delay_time 0 time to delay an internal initiated abort (in seconds) instance_mode READ-WRITE indicates whether the instance read-only or read-write or read-mostly long_module_action TRUE Use longer module and action max_idle_time 60 maximum session idle time in minutes max_iops 0 MAX IO per second max_mbps 0 MAX MB per second ofs_threads 4 Number of OFS threads one_step_plugin_for_pdb_with_tde FALSE Facilitate one-step plugin for PDB with TDE encrypted data optimizer_adaptive_plans TRUE controls all types of adaptive plans optimizer_adaptive_statistics FALSE controls all types of adaptive statistics outbound_dblink_protocols ALL Outbound DBLINK Protocols allowed pga_aggregate_xmem_limit 0 limit of aggregate PGA XMEM memory consumed by the instance remote_recovery_file_dest default remote database recovery file location for refresh/relocate sec_protocol_allow_deprecated_rpcs YES Allow deprecated TTC RPCs standby_db_preserve_states NONE Preserve state cross standby role transition target_pdbs 525 Parameter is a hint to adjust certain attributes of the CDB uniform_log_timestamp_format TRUE use uniform timestamp formats vs pre-12.2 formats
A lot of them are to do with Multitenant. The others? Well, some are fairly obvious, some used to be _underscore parameters. As for the others, I’ll have to wait until I can study the docs.
Oracle Certified Master DBA