If you require a certain number of backups to be retained, you can set the retention policy based on the redundancy option. This option requires that a specified number of backups be cataloged before any backup is identified as obsolete. The default retention policy has a redundancy of 1, which means that only one backup of a file must exist at any given time. A backup is deemed obsolete when a more recent version of the same file has been backed up. For example, you can use the following command to configure a redundancy recovery policy of 2:

CONFIGURE RETENTION POLICY TO REDUNDANCY 2;

When patching an Oracle home, you might run into problems. OPatch might not behave as expected. It is helpful to know where to look for error messages or find additional information to pass on to Oracle Support if you want to log an SR for your problem. So OPatch maintains logs for apply, rollback, and lsinventory operations. The OPatch log files are located in the $ORACLE_HOME/cfgtoollogs/opatch. Each time you run OPatch, a new log file is created, and each log file is tagged with the operation’s timestamp. OPatch maintains an index of processed commands and log files in the opatch_history.txt file – and that is also in the above-mentioned $ORACLE_HOME/cfgtoollogs/opatch directory. So if you change the directory to $ORACLE_HOME/cfgtoollogs/opatch, you’ll see that every time you run OPatch, a log file is created with a date stamp. And then, at the bottom, you’ll see an opatch_history.txt file. look at the file, you’ll see a record of each time you ran the opatch apply, opatch rollback, or lsinventory command. The DBMS_QOPATCH package provides a PL/SQL or a SQL interface to view the installed database patches.

The package returns the patch and patch metadata information available as part of the “opatch lsinventory -xml” command in real-time. So it’s basically a way to see which patches are applied to your database home but from a PL/SQL or a SQL interface. So you basically get an XML-formatted return of your patch information. The DBMS_QOPATCH package allows users to query what patches are installed from SQL*Plus, write wrapper programs to create reports and do validation checks across multiple environments, and also to check patches installed on cluster nodes from a single location. If you log into SQL*Plus as the sys user and then perform select DBMS_QOPATCH.GET_OPATCH_LSINVENTORY from dual. And you’ll see just lots of XML information – which you can use an XML parser to make sense of it.

You query V$INSTANCE_RECOVERY view and consistently receive an OPTIMAL_LOGFILE_SIZE value that is greater than the size of your smallest online redo log file. The OPTIMAL_LOGFILE_SIZE column of the V$INSTANCE_RECOVERY view can be used to determine the appropriate size for all of the online redo log files in your database. If the value of the OPTIMAL_LOGFILE_SIZE column is greater than the size of your smallest online redo log file, you should change the size of all online redo log files to be at least this value. In addition, the FAST_START_MTTR_TARGET initialization parameter simplifies the configuration of recovery time from instance or system failure. After adjusting the size of your online redo log files, you may be able to adjust the value of this initialization parameter for better performance. This is done by rerunning the MTTR advisor after changing the size of your online redo log file to achieve more optimal results. However, running the MTTR advisor is not the best option in this situation for improving instance recovery performance.

 

Starting in Oracle Database 12c, the multithreaded Oracle model enables specific Oracle processes to execute as operating system threads in separate address spaces. Setting up an Oracle database instance for using multi-process multi-thread architecture is done by starting up the Oracle database instance with the THREADED_EXECUTION initialization parameter set to TRUE.

The multi-process multi-thread model requires a password file for SYSDBA authentication while starting the database instance. Without using the SYS password

an  ORA-1031: insufficient privileges error will be triggered on startup.

When the THREADED_EXECUTION parameter is set to TRUE, you must set the DEDICATED_THROUGH_BROKER_LISTENER parameter to ON in your listener.ora file.

When that parameter is set, the listener knows that it should not spawn an OS process when a connect request is received; instead, it passes the request to the database so that a database thread is spawned and answers the connection.

 

 

 

Today, 18th January 2022, The Database patch bundles were released.
All the details on MOS in Doc ID 19202201.9 and Doc ID 21202201.9 are recommended to be installed on production systems.

 

Oracle Groundbreakers EMEA 2021 
Michigan Oracle Users Summit 2021 

Oracle Machine Learning for R (OML4R) is an R API that makes the open-source R statistical programming language and environment ready for enterprise and big data. Designed for significant data problems, OML4R integrates R with Oracle Database.
R users can run R commands and scripts for statistical and graphical analyses on data stored in the Oracle Database. In addition, they can develop, refine and deploy R scripts that leverage the parallelism and scalability of the database to automate data analysis.

For more information, see: https://docs.oracle.com/en/database/oracle/machine-learning/oml4r/1.5.1/tasks.html

The paper below describes an automated system that generates, selects, verifies, and maintains materialized views in the Oracle RDBMS; it presents a novel technique, called the extended covering subexpression algorithm, for the automated generation of materialized views. An extensive set of experiments is described that demonstrates the feasibility and efficiency of this approach. This system has been fully implemented and will be deployed on the Oracle Autonomous Database on the Cloud.

For more information see https://dl.acm.org/doi/abs/10.14778/3415478.3415533

Would you please download and install the one-off patch for your database version and OS for bugs not included in RU yet? If you do not find a patch for your specific version and OS from MOS, please open a Service Request with details on the patch needed. In addition, please include a list of patches already applied (opatch lsinventory -detail) and any other patches you intend to apply.

Some of the Optimizer bug fixes (not all) are controlled by the “_FIX_CONTROL” setting and are DISABLED by default in 19c when installed either through one-off backport or through RUs. Please refer to the corresponding Patch Readme carefully for one-off patches and enable the fixed control to activate the fix.

Example:

SQL> alter system set “_FIX_CONTROL”=”29302565:1”;

V$TRANSACTION lists the active transactions in the system.

(i) The following columns together point to a transaction. (i.e.) The combination of the following should give a unique transaction id for that database.

XIDUSN – Undo segment number
XIDSLOT – NUMBER Slot number
XIDSQN – NUMBER Sequence number

(ii) The following columns explain the number of undo blocks / undo records used per transaction.
USED_UBLK – Number of undo blocks used
USED_UREC – Number of undo records used

In the case of transaction rollback, the above columns will estimate the number of undo blocks that need to be rolled back.

The number of undo records and undo blocks (USED_UREC and USED_UBLK) decreases while the transaction rolls back. When they reach 0, the transaction disappears from v$transaction.

The following query can be used to monitor the transaction rollback.
SELECT A.SID, A.USERNAME, B.XIDUSN, B.USED_UREC, B.USED_UBLK
FROM V$SESSION A, V$TRANSACTION B
WHERE A.SADDR=B.SES_ADDR;

(iii) The STATUS following column explains the status of a transaction.

ACTIVE – Explains the transaction is active.

Before performing a normal/transactional shutdown, YOU can check this view to understand any ACTIVE transactions.
SELECT XIDUSN, XIDSLT, XIDSEQ , SES_ADDR, STATUS FROM V$TRANSACTION;