Unpivot

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One of the sessions at the recent annual UKOUG technical conference (Tech16) was a panel session on optimisation for which I had posted a request for a few advance questions, and one of the questions that appeared in my inbox was as follows: I have a report which is a union all of 27 versions of the statement: select ‘ColumnX_name’… Continue Reading →Read more

Re-registering Databases In A Cluster With srvctl: Problems and Solutions

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Recently I wanted to create a policy managed database in my 12.1.0.2 flex cluster setup, but free servers are not available. Hence I had to unregister an administrator managed RAC database (amdbh12) to make the servers available. Having completed my testing, I dropped the policy managed database and then wanted to drop the database amdbh12 using DBCA… Read more

JSON For Absolute Beginners: Part 5 – Generating JSON in Oracle

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In this fifth article in our series on JSON and the Oracle database we’ll be pulling the curtains back on the magic tricks that can convert your boring old relational data to JSON. OK, maybe that’s overselling it a little. Obviously there’s no magic involved; indeed some may say it’s anything but. But before we get to all of that,… Continue Reading →Read more

Explore Oracle Database In-Memory – Part 2

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Oracle In-Memory is fully compatible with Oracle multitenant database architecture, allowing us to take advantage of fast In-Memory and low-cost storage. This multitenant architecture was also introduced in Oracle 12c, featuring multiple pluggable databases (PDBs) within a container database (CDB). This makes it easy to consolidate databases onto the cloud, deliver a high density of schema-based consolidation without making changes… … Read more

Hacking Indexes

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Indexes are expensive to maintain so we want to get the greatest benefit we can from them and make sure that Oracle uses them whenever it’s appropriate. Sometimes, though, the optimizer seems to ignore indexes that we think would be very effective and when this happens it’s often because the statistics that Oracle has gathered do not reflect the quality… Continue Reading →Read more

JSON For Absolute Beginners: Part 4 – Retrieving JSON in Oracle

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There’s a possibility you’ve parachuted into this series on JSON and Oracle at this point. If you are already familiar with what JSON is and how it is created, and are only interested in discovering how to wrestle JSON data from an Oracle database, then you’re welcome, grab a seat. However, if you see the words JSON and Oracle, and… Continue Reading →Read more

Migrate Oracle Database To ASM Using ASMCMD

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Introduction Oracle Database 10g Release 1 introduced Automatic Storage Management (ASM), a new framework for managing Oracle database files. ASM provides a foundation for highly efficient storage management with direct I/O, redundancy, striping and load balancing. Files stored on ASM are evenly distributed across disks in a disk group and mirrored according to the policies defined in the disk group…. Continue Reading →Read more

Investigating Indexes

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Rebuilding indexes is an activity that you shouldn’t need to do often. There are always a few special cases – like when you’ve moved or recreated a table or if you’ve done a massive delete on a table – when it’s probably a reasonable idea but, in general, there are very few cases where there’s any great benefit to be… Continue Reading →Read more

Explore Oracle Database In-Memory – Part 1

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The Oracle Database In-Memory option was introduced in Oracle 12c (12.1.0.2 patch set). By using the In-Memory option, businesses can benefit from better decisions made in real time, improved productivity, increased competitiveness and lowered costs. The Oracle In-Memory option is designed to fit both Data warehouse and mixed workload OLTP databases, and can be deployed with any existing application that%… Read more

Oracle Database 12.1.0.2c: Hot Cloning Of Pluggable Databases

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Cloning of a Pluggable Database (PDB) in Oracle Multitenant is a great feature and is very useful. Oracle Database 12c Release 1 has introduced various enhancements to the cloning of Pluggable Databases to overcome the limitations imposed by the initial release of Oracle Database 12c (12.1.0.1). In Oracle 12.1.0.2c: PDBs can be hot cloned, i.e. you don’t need to put the source PDB… Continue Reading →Read more

Oracle Database 12.1.0.2c : Hot Cloning of Non-Container Databases

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In the initial release of Oracle 12c (12.1.0.1c), a non-Container Database (non-CDB) could be converted to a pluggable database (PDB) using any of the following methods: Using DBMS_PDB Using datapump (expdb, impdp) Using GoldenGate replication The 12.1.0.2 patchset has introduced the ability to clone a remote non-CDB as a PDB directly over the network. Remote Cloning of a Non-CDB is a… Continue Reading →Read more

Text Indexes

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The Oracle database has many features that are not spoken of frequently and a recent note by Connor McDonald reminded me that there are a couple of notes about optimising Text indexes that have been on my “must write” list for several years. If you’re not familiar with what text indexes can do for you, here’s a thumbnail sketch: create… Continue Reading →Read more

Massive Deletes – Part 4

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In the previous installment of this series I produced some figures highlighting the main differences between doing a large delete by tablescan and doing a large delete by index range scan. Depending on the data patterns involved the correct choice of strategy could make a significant difference to the number of random I/Os, the volume of redo generated, and the… Continue Reading →Read more

JSON For Absolute Beginners: Part 2 – Why Use Oracle?

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In this short series of articles, we’ll be talking about JSON and its integration with the Oracle database.  The first part was an introduction to JSON itself, and was, admittedly, very light on Oracle.  But now it’s probably time to bring Oracle more into the story and talk about how the database has adapted to handle this new format. Or, actually,… Continue Reading →Read more

Incomplete / Complete recovery using RMAN cold backup

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Offline backups (also known as Cold or consistent backups) are taken when the database is in a consistent state, i.e. the database has been shut down with the SHUTDOWN NORMAL, SHUTDOWN IMMEDIATE, or SHUTDOWN TRANSACTIONAL commands. As part of a consistent shutdown, redo has been applied to the data files and the System Change number (SCN) in the data file… Continue Reading →Read more