5 Tips for a Successful Oracle Database Migration

5 Tips for a Successful Oracle Database Migration

Companies need to migrate Oracle data for a long list of reasons, such as moving workloads from on-premises to a cloud or managed hosting environment, implementing a new system, or launching a big data initiative. But whatever their aim, Oracle database migration projects are widely known to pose a major risk of failure and budget overruns. 

A big contributing factor is the misconception that these are simple data-moving operations. In fact, Oracle database migrations are often complex and require careful planning. Data migration services and technology alone are not a guarantee of success.

This post shares five tips for a successful Oracle database migration.

One: Recognize that Oracle database migrations are a business problem.

Any Oracle database migration is a data problem—and therefore a business problem—first, and an IT problem second. Not the other way around as conventionally assumed.

Without engagement from business and technical leaders, the chances of failure are very high. It’s important to get input from management stakeholders and to know upfront that adequate project resources will be allocated.

Too often, a lack of business involvement and commitment results in an Oracle database migration project that is fraught with unknowns and incorrect assumptions. These later manifest as data loading problems, functional testing failures, and other stumbling blocks leading to time and cost overruns. Eleventh-hour emergencies may also lead to engaging third-party Oracle data migration services without adequate due diligence.

Two: Don’t underestimate the scope of your Oracle database migration.

A big reason Oracle database migration projects falter is that they weren’t correctly scoped in the first place. Many organizations underestimate the effort required to migrate an Oracle database successfully. 

Some of the reasons include:

  • Lack of understanding of the current data landscape
  • Lack of awareness of current data quality issues
  • Viewing the migration as a simple data-moving exercise
  • Failure to get input from business stakeholders on their needs during the project
  • Inadequate data migration services, tools, and/or expertise to support the migration

Plus, like many IT-related projects, Oracle database migrations are subject to scope creep and specification changes. The better you can analyze your current data, including its volume, data types, etc., the better you can scope the migration. 

Three: Focus on data quality from the outset.

“Garbage in, garbage out” is an inescapable reality when it comes to data. Why spend money moving data to a new environment or a new application if it isn’t usable? Yet it’s often when an existing database is migrated that errors, gaps, corruption, redundancies, and formatting issues rear their heads. 

Even if the data was acceptable for its prior uses, it might not meet your new objectives, such as access by new applications. A successful Oracle database migration requires an upfront emphasis on delivering accurate data that meets business needs. Finding out at the last minute that data requires cleansing is sure to lead to project delays, budget crunches, and specification changes. 

Four: Leverage appropriate Oracle technology.

From data cleansing to data movement to data governance, purpose-built Oracle technology can help automate your Oracle database migration to save effort and improve consistency and repeatability. Choosing Oracle tools also adds to the value of your Oracle investment.

For example, if you’re moving an on-premises Oracle database to the Oracle Cloud, Oracle offers a wide range of data migration services and tools to help you migrate data into your target cloud service (e.g., Oracle Autonomous Database, Hadoop, or Object Storage). These include:

  • OCI Data Transfer Service, a low-cost data migration service that accelerates moving even large-scale datasets to or from Oracle Cloud.
  • Zero Downtime Migration (ZDM) for more efficient migration of on-premises databases to the Oracle Cloud leveraging high availability technologies like Oracle Data Guard and Oracle GoldenGate. 
  • Oracle Data Pump to move data between Oracle databases via a choice of methods, including in the cloud and between on-premises and cloud.

Five: Leverage appropriate data migration services.

“We don’t know what we don’t know.” Thus, businesses may be unaware of their Oracle database migration challenges until they are blindsided in midstream. 

While data migration services can help reduce time and cost impacts in these situations, they can also be of value upfront by helping you avoid or prepare for them. Data migration services can help you sort out your best options for moving Oracle workloads from your data center to a public cloud platform or managed database hosting provider, for instance. This starts you off on the right foot and helps eliminate risks to project success.

Data migration services can also give you on-demand access to specialized Oracle expertise that many businesses don’t have in-house. Unbiased, third-party experts can save time with valuable insights, as well as champion the best course of action from a range of options.

What’s next?

If you’re thinking of moving Oracle databases to a cloud or managed hosting environment, Buda Consulting can help you choose the best option for your workloads. We can also handle the complete migration process for you, from installing and configuring your new Oracle environment to migrating your data. All while minimizing downtime and business risk.

Contact us for a free “database discussion” to explore your Oracle database migration goals and concerns.

How Poor Communication Brought an Oracle System Down

It was very cold and early on a Monday morning when I received a call from one of my fellow system administrators. He reported that one of our production databases would not come back online after the server hosting the database was restarted. 

Most DBAs would start investigating this issue by looking at database alert logs. But my experience led me to ask my fellow system admin the following question: “What changes did you make on the server prior to the reboot?”

It was his answer to that question that allowed me to quickly understand the issue and fix it in just a few minutes. 

Apparently the system admin (not the DBA) was conducting vulnerability testing and, as a result, made a change to the main listener.ora file that disabled all databases from being able to dynamically register to Oracle database listeners. 

By default, an Oracle database will try to dynamically register to an Oracle database listener on port 1521. This registration process allows connections to the database from outside of the server. The database was online and operational, but because the dynamic registration option was disabled it could no longer register to the listener. So no users could connect to the database.

The fix for this was adding a static listener to the listener.ora for the database hosted on the server, thus allowing it to receive connections. Once the static listener was added, all users were able to connect to the production database without error.

The Technical Problem\

Let’s break this incident down in more detail:

This is the original Listener file 






The administrator added one line (see below in red):







This prevented any databases that do not have a static listener specified in the listener.ora file from accepting connections..

The Technical Solution

To correct the problem, I added a static listener to the listener.ora file (see below in red):














You can find detailed information about the listener file for Oracle version 19c here.

The Communication Problem

We have mentioned in this blog before that almost all problems with technology projects are the result of poor communication. This principle holds here as well. Because the system administrator did not keep any of the DBAs on our team “in the loop” about their vulnerability testing, or the resulting changes, those changes caused production downtime.  

The Communication Solution

Any change to a server, database, or application must be communicated to all responsible parties beforehand. In fact, a better approach in this case would have been to ask the DBA to make the change to the listener file rather than the administrator making the change himself. This would have ensured that an experienced DBA had reviewed the change and understood the potential impact.

The moral of the story is: Keep your DBAs in the loop when you’re making system changes. It’s our job to proactively prevent database issues others might miss.

A Word on Database Security

While an action taken by the system administrator caused a problem in this situation, it should be applauded from a database security standpoint that vulnerability testing was conducted because it exposed a potential vulnerability (the dynamic registration). It is a best practice to disable dynamic registration unless it is necessary for the organization, and unless the associated risk is mitigated by other practices, such as changing the default listener port.  

Database vulnerability testing is a crucial part of a comprehensive IT security plan and is often overlooked. For the reasons described above, the process should always include a member of the DBA team. See a few of our Database Security related blogs here


Database Patch News — February 2021 (Issue 6)

Database Patch News — February 2021 (Issue 6)

Welcome to Database Patch News, Buda Consulting’s newsletter of current patch information for Oracle and Microsoft SQL Server. Here you’ll find information recently made available on patches—including security patches—and desupported versions.

Why should you care about patching vulnerabilities and bugs? Two big reasons:

  • Unpatched systems are a top cyber attack target. Patch releases literally advertise vulnerabilities to the hacker community. The longer you wait to patch, the greater your security risk.
  • Along with running a supported database version, applying the latest patches ensures that you can get support from the vendor in case of an issue. Patching also helps eliminate downtime and lost productivity associated with bugs.

Here are the latest patch updates for Oracle and SQL Server:

Oracle Patches:

January 19, 2021 Quarterly Patch Updates:
21c – Released January 13, 2021, Version 21.1; no Quarterly patch yet

19c – Release Update 19.10 is available (32218494 and 321266828)

18c – Release Update 18.13 is available (32204699 and 32126855)

12cR2 – Release Update 210119 is available (32228578 and 32126871)
Regular support ends in Mar 2023 and extended support ends in Mar 2026.

12cR1 – Release Update 210119 is available (32132231 and 32126908)
Regular support ended in July 2019 and extended support ends in July 2021.

11gR4 – Patch Set Update 201020 is available (31720776)
Regular support ended in October 2018 and extended support ended December 31, 2020.

SQL Server Patches:

SQL Server 2019
Cumulative update 8 (Latest build) Released Oct 1, 2020
Mainstream support ends Jan 7, 2025
Extended support ends Jan 8, 2030

SQL Server 2017
Cumulative update 22 (Latest build) Released Sept 10, 2020
Mainstream support ends Oct 11, 2022
Extended support ends Oct 12, 2027

SQL Server 2016 Service Pack 2
Cumulative update 15 Release date: Sept 28, 2020
Mainstream support ends Jul 13, 2021
Extended support ends Jul 14, 2026

SQL Server 2014 Service Pack 3
Cumulative update 4 Release date: Feb 11, 2019
Mainstream support ended Jul 9, 2019
Extended support ends Jul 9, 2024

SQL Server 2012 Service Pack 4
Release date: Oct 5, 2017
Mainstream support ended Jul 11, 2017
Extended support ends Jul 12, 2022

Note: All other SQL Server versions not mentioned are no longer supported.

4 Keys to Avoiding the Number 1 Cause of Database Project Failure

We all know that database projects and other technical/IT projects often fail. They are never completed, the results fall far short of expectations, nobody uses the new application, and so on.

Why? At the end of the day, if we look beneath the surface-level issues, the main reason for database project failure — by far — is poor communication. 

Case in point: If a project fails because of technical errors or deficiency, It’s either because the technical resources did not have the right skill set, or the requirements that they were working from were incorrect or incomplete.

If it’s the former, then there was a breakdown in communication between the resources and the project manager regarding the set of abilities that the resources have, or there was a breakdown between the project manager and the business analyst regarding what skill sets were needed for the project. If it’s the latter then there was a breakdown in communication between the business analyst and the project manager regarding what the overall system requirements were.

Another typical project failure involves missing deadlines. Typical causes of missing deadlines include resources not being available when needed, or the infrastructure not being ready when it was needed, or the business users not being ready when needed for testing or migration activities. 

Again, in all of these cases the root cause is communication. If one of the parties is not ready when they need to be, it is either because they didn’t know when they would be needed, or they incorrectly stated their availability. If the infrastructure is not available when it is needed, then either the requirements or the deadline for the infrastructure were not properly communicated to the infrastructure team, or the infrastructure team miscommunicated their ability to get the work done in time.

If you look deeper and break down the presenting problems, in almost all cases the root cause of project failures is communication. Often the communication failures occur in the very beginning of the project, during the scoping and estimate or quotation process.

Here are 4 key approaches that I use to mitigate the significant risks to project success caused by poor communication:

  1. When asking someone for a decision on an important point, I always ask twice. If the two answers differ, I ask a third time. And I continue that process until the answers become consistent. If I receive the two different answers from two different critical stakeholders, I will find a reason to send a joint email or have a conversation with both present, and I will re-ask the question in hopes of gaining consensus. (Political sensitivity and tact is critical here… Perhaps that’s the subject of another blog post…)
  2. When nailing down an important decision, I follow up in writing to validate and underscore everyone’s understanding, especially for something for which I have received two different answers over time.
  3. I treat decisions differently than statements of fact. If I ask a client, “Do your customers connect directly to your database?”, this is a statement of fact. There is a right and wrong answer to this question, and it can be validated independently. However, if I ask the customer, “How many customers do you want the database to support in five years?”, this is a decision or a target. There is no right or wrong answer. This cannot be validated except by the same individual (assuming they are the decision-maker).

    I treat statements of fact very differently from decisions/targets:

    • I validate a statement of fact in a variety of ways. I might look at the user accounts on the existing system, or I might ask someone else in the organization, or I might look at the application for clues. 
    • For decisions or targets, validation can be more difficult. As mentioned above, I ask at least twice for any decision that can impact the scope of the project. If the answers differ, or if I feel like the answer is not solid and may change (based on my client’s tone of voice, hesitation, inconsistencies with other statements or requests, or other factors), I will ask again until I am satisfied that the answer is solid.
  4. For all important points that can impact the project time or cost estimate, or the database design or implementation, I always validate them in one fashion or another before we act on them. And if I can’t validate them for some reason, I call them out separately as an assumption in the estimate or quote in order to bring it to the client’s attention and to the team’s attention, and then I mention it directly when reviewing the document with them.

To sum up: as you might expect, the antidote to poor communication is good communication. Especially going into a project, keep the above in mind. Get clarity and validate what you’re hearing. This will make you look good, your customers and technical team members will appreciate it, and your projects are much more likely to succeed.

To get optimum value and results from your database project investments, contact Buda Consulting.

Watch Your FRA!

Watch Your FRA!

When it comes to Oracle database administration, one of the most revered parts of your database structure is the fast recovery area (FRA). This is an Oracle managed area where DBAs usually store some of the following files:

  • Redo logs
  • Archive logs
  • Flashback logs
  • Control files
  • RMAN backups

The purpose of the Oracle FRA is to simplify database recovery. The Oracle database process automatically manages items stored in the FRA and will delete items that are no longer needed. 

Oracle FRA Settings

Now the Oracle FRA may sound like a magical area that should never run into storage-related issues—but that could not be farther from the truth. Even though the Oracle database process will manage items and attempt to delete files that aren’t needed, the DBA also has to be aware of instance settings that may block Oracle from being able to remove the files. Some settings that can cause storage issues with your FRA include:

  • RMAN backup retention setting – If you set your backup retention to store two weeks’ worth of RMAN backups, but your FRA fills up to 100% before any backups can be purged, this will cause your database to halt.
  • RMAN archive log deletion policy – If you set the deletion policy to delete archive logs after they are applied to all standby databases, but haven’t noticed that your primary and standby databases have been out of sync for a long period of time, your FRA can fill to 100% and cause your database to halt.
  • RMAN archive log backup copies setting – By default, backup copies are set to 1. But what if you want to make sure your backups contain more copies of your archive logs in the event that one of your incremental backups became corrupted? When you set this setting higher than 1, you will not be able to delete any archive logs unless they have been backed up however many times this setting is set to. So if you set this option to 3, you will need to have taken at least three backups of each archive log before said log can be deleted from your system. If you opted to store archive logs in your FRA, then this can fill the FRA to 100% and cause your database to halt.
  • Db_flashback_retention_target setting – If you have enabled the flashback database option this is stored in the FRA by default. As with the archive logs, depending on the time value of the setting, it will store all flashback logs needed to guarantee that you can flashback your database as per the setting. If you set this to a high setting, this can fill the FRA to 100% and cause your database to halt.

Those are just a handful of the many ways you can accidentally fill your Oracle FRA, which is why you need to make sure that your FRA is adequately sized to store all files as per all retention settings. You should also create a script that queries the v$recovery_area_usage and have this result sent to the email of all DBAs, as this will tell you how much of your FRA is used and what in particular is taking up the space:

For remote and onsite DBA support to help keep your databases running smoothly, including 24×7 live support, contact Buda Consulting.

Oracle Active Data Guard Replication Error with Cisco Firewall: Root Cause and Workaround

Oracle Active Data Guard Replication Error with Cisco Firewall: Root Cause and Workaround

One of our customers had issues over the past several months with Oracle Active Data Guard replication to a standby server. The database on the standby server would intermittently fall out of sync with the database on the primary server, and log files were not consistently shipping to the standby server. 

Active Data Guard Replication Error

The Oracle database version was running on Oracle Linux 6. The firewall was a Cisco ASA-5585-SSP-40, and the ASA version is 9.6(4)8. 

TNS tracing showed: CORRUPTION DETECTED: In redo blocks starting at block #…

By the time I got involved, the firewall administrators had already implemented all the recommended firewall changes to disable the following:

    •     SQLNet fixup protocol 
    •     Deep Packet Inspection (DPI
    •     SQLNet packet inspection 
    •     SQL Fixup

The following errors were noted in the primary database alert log:

    •     ORA-16055: FAL request rejected 
    •     ARC6: Standby redo logfile selected for thread 2 sequence 33351 for destination LOG_ARCHIVE_DEST_2 
    •     ARC6: Attempting destination LOG_ARCHIVE_DEST_2 network reconnect (12152) 
    •     ARC6: Destination LOG_ARCHIVE_DEST_2 network reconnect abandoned 

The following errors were noted in the standby database alert log:

    •     CORRUPTION DETECTED: In redo blocks starting at block #…
    •     RFS[20]: Possible network disconnect with primary database
    •     Error 1017 received logging on to the standby 
    •     FAL[client, USER]: Error 16191 connecting to…
    •     ORA-16191: Primary log shipping client not logged on standby 

The root cause of the problem turned out to be a bug in the Cisco firewall.  For reasons unknown, when the primary and standby database listeners were using port 1521, the firewall would ignore the settings the admins had implemented for the Oracle Data Guard connections and revert to the default settings. As a workaround, we changed to a different port.

If you are experiencing intermittent or hard-to-diagnose database issues in your environment, contact Buda Consulting.