Oracle Database 12c New Features – Part 2

During this Oracle Database 12c new features series, I shall be extensively exploring some of the miscellaneous, yet very useful, new additions and enhancements introduced in the areas of Database Administration, RMAN, Data Guard and Performance Tuning. Read Oracle Database 12c New Features – Part 1 Part 2 covers: Table partition maintenance enhancements Database upgrade improvements Restore/Recover data file over

During this Oracle Database 12c new features series, I shall be extensively exploring some of the miscellaneous, yet very useful, new additions and enhancements introduced in the areas of Database Administration, RMAN, Data Guard and Performance Tuning.

Read Oracle Database 12c New Features – Part 1

Part 2 covers:

  1. Table partition maintenance enhancements
  2. Database upgrade improvements
  3. Restore/Recover data file over the network
  4. Data Pump enhancements
  5. Real-time ADDM
  6. Concurrent statistics gathering

1. Table partition maintenance enhancements

In Part I, I explained how to move a table partition or sub-partition to a different tablespace either offline or online. In this section, you will learn other enhancements relating to table partitioning.

Adding multiple new partitions

Before Oracle 12c R1, it was only possible to add one new partition at a time to an existing partitioned table. To add more than one new partition, you had to execute an individual ALTER TABLE ADD PARTITION statement to every new partition. Oracle 12c provides the flexibility to add multiple new partitions using a single ALTER TABLE ADD PARTITION command. The following example explains how to add multiple new partitions to an existing partitioned table:

Now lets add a couple of new partitions:

In the same way, you can add multiple new partitions to a list and system partitioned table, provided that the MAXVALUE partition doesn’t exist.

How to drop and truncate multiple partitions/sub-partitions

As part of data maintenance, you typically either use drop or truncate partition maintenance task on a partitioned table.  Pre 12c R1, it was only possible to drop or truncate one partition at a time on an existing partitioned table.  With Oracle 12c, multiple partitions or sub-partitions can be dropped or merged using a single ALTER TABLE table_name {DROP|TRUNCATE} PARTITIONS command.

The following example explains how to drop or truncate multiple partitions on an existing partitioned table:

To keep indexes up-to-date, use the UPDATE INDEXES or UPDATE GLOBAL INDEXES clause, shown below:

If you truncate or drop a partition without the UPDATE GLOBAL INDEXES clause, you can query the column ORPHANED_ENTRIES in the USER_INDEXES or USER_IND_PARTITIONS dictionary views to find out whether the index contains any stale entries.

Splitting a single partition into multiple new partitions

The new enhanced SPLIT PARTITION clause in 12c will let you split a particular partition or sub-partition into multiple new partitions using a single command. The following example explains how to split a partition into multiple new partitions:

Merge multiple partitions into one partition

You can merge multiple partitions to a single partition using a single ALTER TBALE MERGE PARTITIONS statement:

If the range falls in the sequence, you can use the following example:

2. Database upgrade improvements

Whenever a new Oracle version is announced, the immediate challenge that every DBA confronts is the upgrade process. In this section, I will explain the two new improvements introduced for upgrading to 12c.

Pre-upgrade script

A new and much improved pre-upgrade information script, preupgrd.sql, replaces the legacy utlu[121]s.sql script in 12c R1. Apart from the preupgrade checks verification, the script is capable of addressing the various issues – in the form of fixup scripts – that are raised during the pre-post upgrade process.

The fixup scripts that are generated can be executed to resolve the problems at different levels, for example, pre-upgrade and post upgrade. When upgrading the database manually, the script must be executed manually before initiating the actual upgrade procedure. However, when the Database Upgrade Assistant (DBUA) tool is used to perform a database upgrade, it automatically executes the pre-upgrade scripts as part of the upgrade procedure and will prompt you to execute the fixup scripts in case of any errors that are reported.

The following example demonstrates how to execute the scripts:

The above script generates a log file and a [pre/post]upgrade_fixup.sql script.  All these files are located under the $ORACLE_BASE/cfgtoollogs directory. Before you continue with the real upgrade procedure, you should run through the recommendations mentioned in the log file and execute the scripts to fix any issues.

Note: Ensure you copy the preupgrd.sql and utluppkg.sql scripts from the 12c Oracle home/rdbms/admin directory to the current Oracle database/rdbms/admin location.

Parallel-upgrade utility

The database upgrade duration is directly proportional to the number of components that are configured on the database, rather than the database size. In previous releases, there was no direct option or workaround available to run the upgrade process in parallel to quickly complete the overall upgrade procedure.

The (parallel-upgrade utility) that replaces the legacy catupgrd.sql script in 12c R1 comes with an option to run the upgrade procedure in parallel mode to improve the overall duration required to complete the procedure.

The following procedure explains how to initiate the parallel (with 3 processes) upgrade utility; you need to run this after you STARTUP the database in UPGRADE mode:

The above two steps need to be run explicitly when a database is upgraded manually. However, the DBUA inherits the both new changes.

3. Restore/Recover data files over the network

Yet another great enhancement in 12c R1. You can now restore or recover a data file, control file, spfile, tablespace or entire database between primary and standby databases using a SERVICE name. This is particularly useful to synchronize the primary and standby databases.

When there is a pretty long gap found between the primary and standby database, you no longer require the complex roll-forward procedure to fill the gap between the primary and standby. RMAN is able to perform standby recovery getting the incremental backups through the network and applying them to the physical standby database. Having said that, you can directly copy the required data files from the standby location to the primary site using the SERVICE name e.g. in the case of a data file, tablespace lost on the primary database, or without actually restoring the data files from a backup set.

The following procedure demonstrates how to perform a roll forward using the new features to synchronize the standby database with its primary database:

On the physical standby database:

The above example uses the primary_db_tns connect string defined on the standby database, connects to the primary database, performs an incremental backup, transfers these incremental backups over standby destination, and then applies these files to the standby database to synchronize the standby. However, you need to ensure you have configured primary_db_tns to point to the primary database on the standby database side.

In the following example, I will demonstrate a scenario to restore a lost data file on the primary database by fetching the data file from the standby database:

On the primary database:


4. Data Pump enhancements

This part of the section will focus on the important enhancements introduced in data pumps. There are quite a few useful additions, such as converting view into a table while exporting and turning off logging while import.

Turn off redo log generation

The new TRANSFORM option introduced in data pumps import provides the flexibility to turn off the redo generation for the objects during the course of import. When DISABLE_ARCHIVE_LOGGING values is specified with the TRANSFORM option, redo generation for the objects in the context will be turned off during the entire import duration. This feature provides a great relief when importing large tables, and reduces the excessive redo generation, which results in quicker imports. This attribute applies to tables and indexes.

This example demonstrates this feature:

Transport view as table

This is another improvement in the data pumps. With the new VIEWS_AS_TABLES option, you can unload the view data into a table. The following example describes how to unload views data into a table during export:

5. Real-time ADDM analysis

Analyzing past and current database health statuses through a set of automatic diagnostic tools such as AWR, ASH and ADDM is part of every DBAs life. Though each individual tool can be used at various levels to measure the database’s overall heath and performance, no tool can be used when the database is unresponsive or totally hung.

When you encounter an unresponsive database or hung state, and if you have configured Oracle Enterprise Manager 12c Cloud Control, you can diagnose serious performance issues. This would give you a good picture about what’s currently going on in the database, and might also provide a remedy to resolve the issue.

The following step-by-step procedure demonstrates how to analyze the situation on the Oracle EM 12c Cloud Control :

  • Select the Emergency Monitoring option from the Performance menu on the Access the Database Home page.This will show the top blocking sessions in the Hang Analysis table.
  • Select the Real-Time ADDM option from the Performance to perform Real-time ADDM analysis.
  • After collecting the performance data, click on the Findings tab to get the interactive summary of all the findings.

6. Gathering  statistics concurrently on multiple tables

In previous Oracle database editions, whenever you execute a DBMS_STATS procedure to gather table, index, schema or database level statistics, Oracle used to collect stats one table at a time. If the table is big enough, then increasing the parallelism was recommended. With 12c R1, you can now collect stats on multiple tables, partitions and sub partitions concurrently.  Before you start using it, you must set the following at the database level to enable the feature:

In part 3

In part 3, you will learn more on new changes on Cluster, ASM and RAC database.

Read Oracle Database 12c New Features – Part 3