Why Upgrade to Oracle 12cR2? Features, Parameter Changes, and Migration Guide

Oracle 12cR2 Release Overview

Oracle announced the release of 12c Release 2 (12.2) for Linux 64‑bit and Solaris on March 1, 2017, following earlier Exadata and SuperCluster announcements.

Version Number Interpretation

The five‑digit version scheme encodes major release (new software), feature release, middleware version, component patch, and platform/patch identifier. Since January 2016 Oracle also uses a YYMMDD suffix for PSU/SPU/Bundle patches (e.g., 11.2.0.4.180101).

Why Upgrade to 12cR2?

Support for the widely used 11.2.0.4 ends on 31 December 2020 (effectively 31 December 2018 for most customers), leaving roughly 22 months to plan and execute a migration to 12cR2.

New Features in 12cR2

Global Service Manager (GSM/GDS) adds distributed capabilities.

Oracle In‑Memory Option (IMO) provides columnar memory storage for dramatic performance gains.

Multitenant architecture (PDBs) enables consolidation of dozens or hundreds of databases.

Sharding, introduced in 12cR2, offers a distributed database model built on the GDS component.

Parameter Landscape

Oracle’s total parameter count has grown rapidly: 10.2.0.5 has 1 618 parameters (259 visible), 11.2.0.4 has 2 912 (351 visible), 12.1.0.2 has 3 975 (380 visible), and 12.2.0.1 has 4 845 (417 visible). Only about 10 % are exposed via SHOW PARAMETER, indicating a large set of hidden, default‑optimal settings.

Key Parameter Recommendations

DEFERRED_SEGMENT_CREATION – default TRUE, set to FALSE.

_DATAFILE_WRITE_ERRORS_CRASH_INSTANCE – default TRUE, set to FALSE.

JOB_QUEUE_PROCESSES – default 1000; adjust to actual need or set to 0 if unused.

_OPTIMIZER_AGGR_GROUPBY_ELIM – default TRUE, set to FALSE to avoid GROUP BY errors.

SESSION_CACHED_CURSORS – default 50; increase to around 1000 to reduce memory fragmentation.

Upgrade Path

Migration involves a structured process: initial assessment, solution design, testing, and production rollout. Detailed step‑by‑step procedures are available in DBAplus community articles referenced throughout the original newsletter.

Overall, the article provides a comprehensive overview of Oracle 12cR2’s new capabilities, the explosion of database parameters, and practical guidance for planning and executing an upgrade.