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The new CS_SESSION package and DB_NOTIFICATIONS view in the Autonomous Database

In Autonomous, DBA, Oracle database on January 20, 2022 at 09:19

Two new objects have been recently introduced in the Oracle Autonomous Database on Shared Exadata Infrastructure.

1. The first one is the CS_SESSION package.

When you open a connection to the Autonomous Database, that session is assigned a consumer group. But consumer groups affect the concurrency and the DOP (degree of parallelism). HIGH service is run in parallel while LOW service runs in serial. So for example, if you have a PL/SQL procedure or function that has to execute statements in the same session with changing consumer groups, the way is to use the new CS_SESSION.SERVICE_NAME procedure.

The number of concurrent statements run in the database depends on 2 factors: the type of the service name and the numbers of the Oracle CPUs provisioned for the ADB:

The new package CS_SESSION contains only one procedure: SERVICE_NAME. My current version is 19.14, I am not sure if the package/procedure is included in all lower RUs. Most likely it is.

The valid values accepted as an IN parameter are: HIGHMEDIUMLOWTP and TPURGENT.

After running the procedure, Oracle does not reset any session attributes. Anything the user set for their session before calling this procedure will continue as-is. 

The ADMIN user is granted EXECUTE privilege on CS_SESSION with GRANT OPTION. The privilege is also granted to DWROLE without the GRANT OPTION.

Here is how to change the consumer group from LOW to TPURGENT:

You might get the following error:

ORA-02097: parameter cannot be modified because specified value is invalid ORA-01031: insufficient privileges ORA-06512: at “C##CLOUD$SERVICE.CS_SESSION”, line 142

Note there is an open bug for this.

You can create an AFTER SET CONTAINER trigger if you would like to limit the values a user can set for the consumer group session. You might not want that all users can set to TPURGENT but allow them go with TP only.

2. The second new object is the DB_NOTIFICATIONS view which stores information about maintenance status notifications and timezone version upgrade notifications for the ADB instance. Let us describe the view

and check what is in it:

As we can see there was a patch run on the data dictionary and there is another maintenance scheduled for the 19th of January.

3. Good to know that we can now use GitHub Raw URLs with DBMS_CLOUD APIs to access source files that reside on a GitHub Repository.

4. Also, the DBMS_PIPE package is now available in the Autonomous Database.

Moving Autonomous Databases across regions

In Autonomous, DBA, OCI, Oracle database, Replication on January 3, 2022 at 13:26

With the new OCI regions, we might want to move our databases to a closer location – in my case moving my databases from Frankfurt to Stockholm.

First what comes to mind is to enable Autonomous Data Guard and then switch over. However, you need a paired region – we cannot create a standby database just anywhere:

The list of Autonomous Data Guard Paired Regions shows that for each Source Region, we have 1-4 Paired Regions.

You need to be subscribed to a region before it can appear on the list and use it. And note: once you subscribe, there is no unsubscribe! You will need to apply for a limit increase.

I am told that soon, once a good standing payment history has been established, you will be eligible for unlimited regions. 

Another option is simply to create a clone:

Note that if you are using a clone from a backup, you cannot have the clone in another region, no idea why not! As you can see from the screenshot below, I am not getting a drop down list of regions:

So, let us create the database clone in Stockholm from the current AEG database running in Frankfurt:

Once the database is cloned, you can optionally terminate the copy in Frankfurt. But do not do it before you have verified the new clone as you might get an (unknown) error, something like this:

In case you do not want to deal with support, just create a new database and move the data with Data Pump.

My home region is Germany Central (Frankfurt). So am I able to change now my home region to Sweden Central (Stockholm) instead of Germany Central (Frankfurt)? Alas, this is not possible. Not yet at least.

According to the Metalink document Change Home Region in OCI console (Doc ID 2389905.1), the home region of the tenancy is fixed at creation time and cannot be moved. If you still wish to have the region changed, the only way to get it done would be to re-create the tenancy. That would mean removal of the current tenancy with all its resources and creating a new one.

Having the primary database in one region and a standby database in another is good practice in terms of DR. Even more complex scenarios are available. How about having a sharded Oracle Database spread among OCI, AWS and Azure? Possible but I would avoid such a complexity.

Operating System access from within the Autonomous Database

In Autonomous, DBA, Oracle database, OS on December 1, 2021 at 09:47

Oracle Autonomous Database does not let us access the operating system. Not even DBA access is allowed.

So, how can we view the content of ADB log or trace files from the OS? How about the alert.log file? “Not needed as all is autonomous” is the common answer. But that is not good enough for most DBAs.

Since September 2021, SQL Trace is supported in the Autonomous Database. If DBAs enable SQL Trace, the same tracing information saved to the trace file on Cloud Object Store is available in the SESSION_CLOUD_TRACE view in the session where the tracing was enabled.

When you enable SQL Tracing, the same trace information that is saved to the trace file on Cloud Object Store is available in the SESSION_CLOUD_TRACE view in the session where the tracing was enabled.

But how about other trace files? It is still possible via Oracle’s internal views. In fact, we don’t have access directly to the V_$ views but rather to their V$ synonyms.

Full access is available to V$DIAG_OPT_TRACE_RECORDS, V$DIAG_SQL_TRACE_RECORDS, V$DIAG_SESS_SQL_TRACE_RECORDS and V$DIAG_SESS_OPT_TRACE_RECORDS.

The names of the trace files and their content is visible through V$DIAG_TRACE_FILE_CONTENTS:

We can see the contents of a a given trace file, say eqp12pod2_p009_193404.trc. The file has 253 lines, so here is a screenshot from the top of the file content:

We can view the latest trace files generated by the database from V$DIAG_TRACE_FILE:

Here are a couple of blog post and articles related to the topic:

How about the alert.log file? The content is in X$DBGALERTEXT:

select to_char(ORIGINATING_TIMESTAMP,'YYYYMMDD-HH24:MI:SS'), MESSAGE_TEXT
from X$DBGALERTEXT
order by RECORD_ID;

However, in ADB, we do not have access to X$DBGALERTEXT. Good news is that we have access to V$DIAG_ALERT_EXT which shows the contents of the XML-based alert log in the Automatic Diagnostic Repository (ADR) for the current container (PDB). V$DIAG_ALERT_EXT which came in 12.2 is sort of a subset of X$DBGALERTEXT. Here is how you can search for ORA- errors. Use:

SELECT ORIGINATING_TIMESTAMP, MESSAGE_LEVEL, MESSAGE_TEXT, PROBLEM_KEY
FROM V$DIAG_ALERT_EXT
WHERE MESSAGE_TEXT LIKE '%ORA-%' AND ORIGINATING_TIMESTAMP > sysdate-7
ORDER BY ORIGINATING_TIMESTAMP DESC;

to find the ORA- errors during the past week.

Possible level message values are:

1: CRITICAL: critical errors
2: SEVERE: severe errors
8: IMPORTANT: important message
16: NORMAL: normal message

And here is how to see the top of the alert.log file content from the last 24 hours:

SELECT to_char(ORIGINATING_TIMESTAMP,'DD.MM.YYYY-HH24:MI:SS')||': '||MESSAGE_TEXT as "alert.log"
FROM V$DIAG_ALERT_EXT
WHERE ORIGINATING_TIMESTAMP > sysdate-1
ORDER BY ORIGINATING_TIMESTAMP DESC;

Regardless of the fact that we do not have server OS access, we can still create directories from within the Autonomous Database.

CREATE DIRECTORY creates the database directory object and also creates the file system directory if it does not already exist. If the file system directory exists then CREATE DIRECTORY only creates the database directory object.

It is possible also to create subdirectories. For example, the following command creates the database directory object version_patches and the file system directory version/patches:

CREATE DIRECTORY version_patches AS 'version/patches;

You can list the contents of a directory in the Autonomous Database by using the function DBMS_CLOUD.LIST_FILES.

The following query lists the contents of the VERSION directory:

SELECT * FROM DBMS_CLOUD.LIST_FILES('VERSION');

You can copy Files Between Object Store and a Directory in Autonomous Database.

Starting with Oracle Database 21c, Data Pump can perform exports from Oracle Autonomous Database into dump files in a cloud object store.

Thus, now we can easily migrate data out from an Oracle Autonomous Database and import it into another location.

Here is an example assuming that we have already created the credential_name JMD_OBJ_STORE_CRED:

Details on how to create the credentials can be found in the Oracle Cloud Infrastructure User Guide which has “only” 5952 pages!

Beware Bug 33323028 – DATA PUMP EXPORT TO OCI OBJECT STORAGE FAILS – present even in 21.4 – Object store ODM Library is not enabled by default – How To Setup And Use DBMS_CLOUD Package (Doc ID 2748362.1)

Conclusion: as you can see the OS access is close to zero. There are very few views that let us see what is residing on the the operating system. What I like most is (1) the possibility to run SQL Trace, (2) being able to view the contents of the XML-based alert log and (3) the ability to run an export directly from object store (21c and above). I would like to see access to X$DBGALERTEXT.

Simple Oracle Document Access (SODA) in the Autonomous JSON Database

In Autonomous, DBA, OCI, Oracle database on November 12, 2021 at 12:09

“I ordered a soda – caffeine-free, low sodium, no artificial flavors. They brought me a glass of water.” – Robert E. Murray

SODA is a set of NoSQL-style APIs that let you create and store collections of documents in Oracle Database, retrieve them, and query them, without needing to know Structured Query Language (SQL) or how the data in the documents is stored in the database.

Oracle database stores, manages, and indexes JSON documents, and developers can access these via document-oriented APIs in a NoSQL style.

A recent white paper written by Vlad Kamys, Francesc Mas and Sai Penumuru explained how to modernize your applications and increase business resilience and security with JSON on Oracle Database, and new cloud-based Oracle Autonomous JSON Database.

Here are few examples on how to use JSON and SODA in the Oracle Autonomous Database.

From the Tools tab, start “Database Actions”, and then select “SQL”:

The following below are typical SODA commands:

(1) list the collections

(2) create the EMP collection

(5), (6) and (7) insert three JSON documents into the collection

(10) gets all documents where the name is “Francesc”

(11) gets all documents where the salary is greater than 300

(12) gets all documents where the jobs starts with “D”

(13) gets all documents where the jobs contains the string “play”

Here is the output from command extracting all documents where the jobs starts with “D”:

If we do not have a text index on “job”, then we get an ORA-40467:

We can also run standard SQL on the EMP table which gets created as a result of creating the collection:

Here is how to get the output from EMP by using JSON_VALUE:

You can think of SODA as a programming bridge between the NoSQL model and the relational model.

There is also the DBMS_SODA package in the database. You can drop the EMP collection simply with “soda drop emp” but you can also run select DBMS_SODA.DROP_COLLECTION(’emp’) from dual; The function will return 1 when it succeeds and 0 when it fails.

Work with JSON Documents in Autonomous Database provides examples of how Java code opens a SODA collection of cart documents, how to use SQL with a SODA collection, etc.

Finally, there is JSON DB/SODA DB Health-Check Script that is a tool developed by Oracle Support Services. The tool, also known as jsonsodadb_hc, is used to check the environment in which a single SQL statement runs, checking for the current status of JSON DB and SODA DB components, makes recommendations based on current settings and checks if the components are being used.

SQL Trace and X-ADG in the Oracle Autonomous Database

In Autonomous, DBA, OCI, Oracle database, Replication on October 6, 2021 at 09:12

Two very different in nature but equality useful features are now available in the Oracle Autonomous Database:

  1. SQL Tracing in Autonomous Database
  2. Cross-Region Autonomous Data Guard in ADB-S

Here is how to enable and use them:

SQL Trace in ADB:

You need first a standard bucket as SQL tracing files are only supported with buckets created in the standard storage tier. Also, create a token (you can have at most 2 tokens) and do not use your OCI password when creating the credentials.

Next, you have to create a credential for your Cloud Object Storage account. Note the full username below – do not simply use the one with what you login to the console.

BEGIN
  DBMS_CLOUD.CREATE_CREDENTIAL(
    credential_name => 'JULIANDON_CREDENTIAL',
    username => 'oracleidentitycloudservice/juliandon@yahoo.com', 
    password => 'generated_token'
);
END;
/

PL/SQL procedure successfully completed.

Afterwards, set the init.ora parameters DEFAULT_LOGGING_BUCKET to specify the Cloud Object Storage URL for a bucket for SQL trace files:

SET DEFINE OFF;
ALTER DATABASE PROPERTY SET 
   DEFAULT_LOGGING_BUCKET = 'https://objectstorage.eu-frankfurt-1.oraclecloud.com/n/juliandon/b/adbkofa/o/';

Database altered.

Next, specify the credentials to access the Cloud Object Storage. Note that although I am doing this as the ADMIN user, I still have to prefix the credential with ADMIN. Otherwise, you get an error message.

ALTER DATABASE PROPERTY SET DEFAULT_CREDENTIAL = 'ADMIN.JULIANDON_CREDENTIAL';

Database altered.

Before we can enable SQL trace, we configure the database to save SQL Trace files:

exec DBMS_SESSION.SET_IDENTIFIER('sqltrace_jd');

PL/SQL procedure successfully completed.

exec DBMS_APPLICATION_INFO.SET_MODULE('module_jmd', null);

PL/SQL procedure successfully completed.

ALTER SESSION SET SQL_TRACE = TRUE;

After running the SQLs, disable SQL tracing so that the collected data for the session is written to a table in your session and to a trace file in the bucket you configured when you set up SQL trace.

ALTER SESSION SET SQL_TRACE = FALSE;
ALTER DATABASE PROPERTY SET DEFAULT_LOGGING_BUCKET = '';

The SQL Trace facility writes the trace data collected in the session to Cloud Object Store in the following format:

default_logging_bucket/sqltrace/clientID/moduleName/sqltrace_numID1_numID2.trc

When you enable SQL Tracing, the same trace information that is saved to the trace file on Cloud Object Store is available in the SESSION_CLOUD_TRACE view in the session where the tracing was enabled.

SELECT trace FROM SESSION_CLOUD_TRACE ORDER BY row_number;

After you close the session, the data is no longer available in SESSION_CLOUD_TRACE.

DESC SESSION_CLOUD_TRACE

Name       Null? Type
---------- ----- ------------------------------
ROW_NUMBER       NUMBER
TRACE            VARCHAR2(32767)

Check Connor McDonald’s blog entitled SQL trace on your cloud database.

Cross-Region Autonomous Data Guard in ADB-S

Autonomous Data Guard provides a standby database instance in a different availability domain in the same region or in a standby database instance in different region.

If you create the standby database in the current/local region and if the primary instance becomes unavailable – the Autonomous Database automatically switches the role of the standby database to primary and begins recreating a new standby database.

ADB currently supports up to 2 standby databases – a local one in the same-region and an additional one which is remote – called cross-region.

So, with the new cross-region standby database, you can perform a manual failover to the standby database if the current region goes down.

A detailed blog by Nilay Panchal entitled Cross-Region Autonomous Data Guard – Your complete Autonomous Database disaster recovery solution! covers in detail how to create the remote standby database and how to manually switch over.

Note that each region has one or a few nearby paired regions in which a remote standby may be created. As you can see from the screenshot above my tenancy in Frankfurt is subscribed to 3 remote regions in which I can create a remote standby.

It is important to know that ADB-S does not allow us access to the standby databases but after a switchover or failover, the database wallet downloaded in the primary database region can be used in the remote region.

It is extremely simple to manually switchover to the other region – in my case from Frankfurt to Zurich, just with a click of a button:

Simple and elegant!

Life, Grace and Rollover time of passwords in the Oracle Database

In DBA, Oracle database, Security and auditing on August 6, 2021 at 10:26

The latest Release Update of Oracle Database 19c, namely 19.12, comes with two new features: Oracle memory speed support for PMEM devices and gradual database password rollover for applications. The gradual database password rollover is backported from Oracle 21c.

I still remember very well the times when changing the password of a databases schema/user required shutting down both the database and the application and this practice has not really changed much until now. You can change database credentials without downtime thanks to proxy users:

Password rolling change before Oracle 21c

With the latest RU of 19c, there is a way to do this online. And of course also with 21c.

Now, there is a password rollover time period when the user can log in using either the old password or the new password. Here is how it works.

Oracle Database 19.12 introduces a new parameter related to the already existing PASSWORD_LIFE_TIME and PASSWORD_GRACE_TIME parameters called PASSWORD_ROLLOVER_TIME.

Note the default and the minimum and maximum values for the 3 parameters above. All numbers show days.

In order to enable the feature, we have to modify first the user profile with a non-zero limit for PASSWORD_ROLLOVER_TIME. This allows the database password of the application user to be changed to a new one and at the same time the old password can be used for the time specified by the PASSWORD_ROLLOVER_TIME. During the rollover period of time defined by PASSWORD_ROLLOVER_TIME, the application user/schema can use both the old password and the new password. When the rollover time expires (that is 1a), only the new password can be used.

After a password is created for a new user or the password is being changed, then the password follows a life cycle and grace period in four phases: 1a&1b, 2, 3 an 4:

We can query DBA_USERS to find the user’s account status from the ACCOUNT_STATUS column (check the screenshot on the top of the post). It is important to point out that after the rollover period has begun, we can still change the password: with or without the REPLACE clause. The rollover start time is fixed at the time when the user changes the password. The start time is not affected by further password changes during the password rollover period. 

Here is how I could connect to the database with 2 different passwords after the initial profile re-configuration:

If needed, we can quit the rollover time period at any time with the following command:

ALTER USER JULIAN EXPIRE PASSWORD ROLLOVER PERIOD;

We cannot configure the gradual database password rollover for the following connection types:

  • Direct logins for Oracle Real Application Security users
  • Kerberos-, certificate-, or RADIUS-based externally authenticated connections
  • Centrally managed user (CMU) connections
  • Administrative connections that use external password files
  • The Oracle Data Guard connection between the primary and the standby

For more on the topic check Rodrigo Jorge’s post Gradual Database Password Rollover brings new backdoor opportunities to find out how to prevent from possible hackers when using this new feature or if interested in the internals, check Understanding internally how 21c Gradual Database Password Rollover works.

A good example on how to use the feature is given by Mouhamadou Diaw in his blog post Oracle 21c Security: Gradual Database Password Rollover

And here is something from Oracle v4:

DBAs: 20 years after

In DBA, Oracle database on June 28, 2021 at 16:37

Oracle 9i was released 20 years ago. Oracle Real Application Clusters (RAC) and Oracle XML DB were cool new things except for a few OPS DBAs who even stopped playing ping-pong if you know what I mean.

Now, Oracle 21c is available from the public cloud and and several other database brands are competing shoulder to shoulder with the Oracle database.

However, DBAs still go their separate own ways, just like at the end of the book “20 years after” by Alexandre Dumas.

Some are still focused mostly into on-premises database work, some are very cloud oriented and some are positioning themselves into the golden middle. Just like the Three Musketeers.

The DBA profession still stays the same: solid, desired by IT experts and for good or for bad – still arguably the most complex job in IT. Complex in both cloud and off-cloud.

In a recent study, the DBA profession is #7 in Best Technology Jobs, #19 in Best STEM Jobs and #55 in the top 100 Best Jobs:

According to the study, Database Administrators made a median salary of $93,750 in 2019. The best-paid 25 percent made $120,880 that year, while the lowest-paid 25 percent made $68,340:

As we all know, it is still not all about the money… So, let us look at the rest.

Upward Mobility, meaning opportunities for advancements and salary are “Above Average”, same is the Stress Level, meaning work environment and complexities of the job’s responsibilities. But the Flexibility which means an alternative working schedule and work life balance is rated as “Average”.

I personally think that all 3 categories above are well rated, however there is another category called Job Security which totally depends on the DBA – it cannot be generalized.

It is worth reading Tim Hall’s What Employers Want : A Series of Posts and Learning New Things : A Series of Posts.

If you would like to know what will change, what new skills are required and how to work in hybrid environment, check The Cloud and Database Administration by Craig S. Mullins.

The Next Generation of DBAs is well described in Cloud DBA: The Next Generation of Database Administrator?

A DBA should be nowadays master of at least few database brands. There are several list and websites pointing towards the top/best databases but imho every database has its use cases and clients. Here are few:

Top 15 databases to use in 2021

Top 25 Best Database Management Software in 2021

6 Best Databases To Use In 2021

Best database software in 2021

And this one is from today, June 28th, 2021: Top 30 Most Popular Database Management Software: Complete List

Let me point out at the end that the Database field is rapidly changing – cloud native databases, NewSQL, etc. so DBAs are even more and more important. The application architecture is getting more diverse because of cloud and the newly emerging databases plus the transformation of traditional databases – think of Oracle Autonomous Database for instance.

As a DBA, there is always a database you like and prefer more than another one but once you are comfortable with the work you are doing, either on-prem or in the cloud – enjoy, learn new things and look into the future remembering you have chosen one of the best professions in the world!

Licensing Types of the Oracle Database

In Cloud, Database options, Databases, DBA, New features, Oracle database on May 16, 2021 at 13:18

After being asked on daily basis all kinds of questions on Oracle Database Licensing, as time goes by, you sort of understand it. Sort of, because the Oracle Database Licensing Guide is 602 pages long and gets often updated. The latest one is from April 2021 – now it is mid-May.

Moreover, you have perhaps seen all Oracle certifications but if you search for one on licensing you will find what I did – there isn’t one.

What I am trying to do now, is to summarize Database Licensing in a short blog post – this might be helpful for many to at least understand the concept.

There are 3 types of licenses for the Oracle Database: Packs, Options and Features and 9 Oracle Database Offerings: Standard Edition 2, Enterprise Edition, Oracle Database Appliance, Exadata, Exadata Cloud Service and Cloud@Customer, Database Cloud Service Standard Edition, Database Cloud Service Enterprise Edition, Database Cloud Service Enterprise Edition – High Performance and Database Cloud Service Enterprise Edition – Extreme Performance (you can see their abbreviations in the table below).

  1. Packs: there are 5 different packs for the Oracle Database:

2. Options: there are 15 database options for the Oracle Database:

  • Oracle Active Data Guard
  • Oracle Advanced Compression
  • Oracle Advanced Security
  • Oracle Database In-Memory
  • Oracle Database Vault
  • Oracle Label Security
  • Oracle Machine Learning
  • Oracle Multitenant
  • Oracle On-Line Analytical Processing (OLAP)
  • Oracle Partitioning
  • Oracle RAC One Node
  • Oracle Real Application Clusters (Oracle RAC)
  • Oracle Real Application Testing
  • Oracle Spatial and Graph
  • Oracle TimesTen Application-Tier Database Cache

Here are the ones related to Consolidation, HA, Managability and Performance:

3. Features: there are 131 features that can be licensed with the Oracle Database out of which 105 are for EE and 123 are for Exadata. As you can see, there are 3 features available for Exadata, ExaCS and ExaC@C falling under the functional category of Autonomous:

If you would like to drill down in detail, use the Database Feature and Licensing tool which is available online without the need to register or have an Oracle account.

Moreover, the Oracle Enterprise Manager Licensing Manual is 366 pages, so there is more to read if you are done with the Database Licensing Manual.

You might think that is way too much for me, and perhaps it is, but the situation is very similar with other database vendors. Let us look at AWS and GCP for instance:

AWS have more than 10 database offering:

Amazon Aurora
Amazon RDS
Amazon Redshift
Amazon DynamoDB
Amazon ElastiCache
Amazon DocumentDB (with MongoDB compatibility)
Amazon Keyspaces (for Apache Cassandra)
Amazon Neptune
Amazon Timestream
Amazon Quantum Ledger Database (QLDB)
AWS Database Migration Service (DMS)

GCP have also more than 10 database offerings:

Relational: Bare Metal Solution for Oracle workloads
Cloud SQL: Managed MySQL, PostgreSQL and SQL Server
Cloud Spanner and BigQuery
Key value: Cloud Bigtable
Document: Firestore and Firebase Realtime Database
In-memory: Memorystore
NoSQL: MongoDB Atlas and managed offerings from open source partner network including MongoDB, Datastax, Redis Labs, and Neo4j

And, after all, Azure are not much behind:

Azure SQL Database
Azure SQL Managed Instance
SQL Server on Virtual Machines
Azure Database for PostgreSQL
Azure Database for MySQL
Azure Database for MariaDB
Azure Cosmos DB
Azure Cache for Redis
Azure Database Migration Service
Azure Managed Instance for Apache Cassandra

After all, being expert in database licensing in a skill of its own!

Applying one-off patches in the Cloud on Oracle Database 21c

In Cloud, DBA, OCI, Oracle database on April 27, 2021 at 08:37

Oracle have just released new fixes for the 21c version of database release: a security fix and a JDK bundle patch.

The recommendation is to apply these two patches mentioned below to your databases:

• 32640471 21C SECURITY FIXES FOR CPUAPR2021
• 32685286 JDK BUNDLE PATCH 21.0.0.0.210420

Most likely, you will first get an email from Oracle to let you know that the patches are already available:

How to apply the patch? The one-off patches (now they are call interim patches) can be applied via the Console, API or even manually. To apply an interim patch manually, you can use the Opatch utility. The detailed steps are provided in the Applying one-off patches on Oracle Database 21c documentation. The patches can be applied in any order.

Here is how simple and easy it is:

1. For the database on which you want to apply the patches, just click its name to display details and under Resources, click Updates:

2. Click on “Apply a one-off patch“:

3. Then, in the Apply one-off patch dialog, enter the patch numbers. Use a comma-separated list to enter more than one patch. I did apply them one after each other. Paste the patch number and then click Apply.

While the patch is being applied, the database’s status displays as Updating:

A work request is created for the patching operation allowing us to monitor the progress of the operation.

If the operation completes successfully, the database’s status changes to Available:

It is that simple!

Migrating databases with several database links

In Cloud, Consolidation, Databases, DBA, Oracle database, Replication on April 1, 2021 at 09:08

In a couple of recent database migration cases, one of the main questions raised, was how to figure out all outgoing and incoming database links as they have to be modified after the massive migrations.

DBLINKS5

Outgoing database links is simple: DBA_DB_LINKS describes all database links in the database. And this view has been part of the database (at least) since 7.3.4

The tricky part is how to find all incoming database links. At least before 12.2, where a new view called DBA_DB_LINK_SOURCES, shows the information of the source databases that opened database links to the local database.

So, how about the databases that are version 12.1 and below?

An Oracle community discussion on the MOS DBA forum gives several ideas:

Option 1: Bruno suggests to “start from the listener logfile; with some “awk/sed/vi” work it should be possible to extract the list of “origins” of the connections… -> From this list, identify the database servers -> Search database links on relevant databases on these servers”.

Might work but might be rather tedious work if there are 100s of different servers.

Option 2: Brian suggests “to query V$SESSION to see active sessions from the other database server. Hint…look at the MACHINE column to see if it matches the other database server name. Querying V$SESSION will only work if the link is open when you query it. As such, you may want to add an AFTER LOGON trigger which writes an audit entry to a table if the connection is from that database server.”

If you create a logon trigger to insert all incoming connection via database link note that in 11g, you can do that using value sys_context(‘USERENV’,’DBLINK_INFO’) which will give us all information. But check first Doc ID 2593966.1 as there is Bug 18974508: sys_context(‘userenv’, ‘dblink_info’) returns incomplete information.

But before 10g, there is no DBLINK_INFO, we we must use x$k2gte:

 
select username, osuser, status, sid, serial#, machine,
process, terminal, program from v$session
where saddr in (select k2gtdses from sys.x$k2gte);

The above is documented in Doc ID 332326.1: How to identify a session started by a remote distributed transaction? The fixed table x$k2gte contains 2PC Global Transaction Entry. The column k2gtdses in x$k2gte has the session state object and this can be mapped to the saddr column of v$session.

But as explained by Mark, the problem is that until the trigger finishes the session the remote db link session is not considered to exist and only upon successful session connection does Oracle then go and update related facts about the session.  Oracle does not guarantee read consistency on v$ views and the v$ views are based on x$ tables which are really program storage areas.  These areas get updated at various points in the logic.  It is possible that a logon trigger may not work in this specific case.  An alternate approach would be to run a process every N time that just snapshots what is out there and records new remote queries.  After all you really only need one capture per remote source whether you care about only database links or care about each client server.

One of the top database experts, Mariami Kupatadze, gave us a very elegant way of how to find remote sessions executing over a database link using x$k2gte, x$ktcxb, x$ksuse and v$session_wait in a single SQL statement.

A more detailed version called Identifying database link usage was written by John Hallas in 2015.

Long story short: for databases from 7.3 till 12.1 create a job capturing the distributed transactions based on the script given in Doc ID 104420.1 “Script to show Active Distributed Transactions”. And you can modify the scripts if not only the active remote transactions need to be captured. For 12.2 and after, just use the view  DBA_DB_LINK_SOURCES. 

create_database_link