Category Archives: Databases

Spring Data : HikariPool-1 – Connection oracle.jdbc.driver.T4CConnection@456d6c1e marked as broken because of SQLSTATE(08003), ErrorCode(17008)

By | December 14, 2025
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In an application using Spring Data I noticed frequent Warning lines and shaky behaviour, even locking with the following message. This is a Connection Eviction Warning. In simple terms, your application (using HikariCP) tried to use a database connection that it thought was valid, but when it reached out to the Oracle database, it found… Read More »

Bash one liner: Fix Grafana SqLite

By | May 19, 2025
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At times when closing Grafana with a kill command SqLite can get corrupted. This is the one liner that saves the day:

Clean #Oracle schema used space after an archival

By | May 13, 2025
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When archiving a big database it is very important to free up space after that. After running the archival scripts that basically deleted old data from the production database, some extra steps were necessary to actually clean up the used space in the database. To first check how much space we still use after deleting… Read More »

Read text content of a blob in #Oracle SQL

By | May 13, 2025
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Sometimes you need to inspect the content of a text blob in Oracle. Yes, if the content is not a text then this does not make sense, but often times we insert in a blob field a really long text like an XML content or JSON content of a document. What we need to do… Read More »

#Oracle # SQL Covert view to table issue: ORA-01723: zero-length columns are not allowed

By | July 31, 2023
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In an Oracle database I was trying to convert an existing view to a table and preserve the data in it. For most of my views the following SQL worked perfectly: Then in one on the instances the following error occurred: While inspecting the SQL code of the views I noticed that the view with… Read More »

Activate #infinispan second level cache with #jboss and #hibernate

By | November 23, 2022
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Second level cache is an extremely powerful way to improve performance of an enterprise application if done right. In the following I will explain how to activate and configure second level cache when using Hibernate and Jboss 7.4+ application server. Jboss 7.4 comes with Infinispan as the build in second level cache solution. This makes… Read More »

#Oracle quick way to investigate slow or time consuming application queries

By | November 21, 2022
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In the following post I will describe my quick procedure I always use to debug the database queries generated by an application that hit an Oracle database. In a lot of cases your queries that hit the database are not written explicitly by a developer. That may be the case when intermediate layers as Hibernate… Read More »

#SQL #Oracle : Move all indexes to a different tablespace

By | October 18, 2022
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In general is good to have a separate tablespace for your index tables. Sometimes the default tablespace, in our case DATA, is used by an application using hibernate layer to automatically create all the tables and indexes. Then the issue is how to move the automatically created indexes to the special created tablespace for indexes,… Read More »

#Oracle ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn]

By | November 2, 2021
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Oracle 11g database with Data Guard active. A switch of the sites (from production to disaster recovery node) is done and all seems good. Suddenly one day after the switch (more than one month) the enterprise application using it cannot connect any-more (connection pool getting filled up). The underlying issue that causes this is reported… Read More »

#Oracle: #SQL to get the latest executed queries in a schema

By | February 20, 2021
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I was trying to obtain the last executed query on an Oracle instance. Seems easy but I wanted also: to exclude the queries that are done by sys user as maintenance to focus on queries executed by a specific client type. The best way to do it is to use the V$SQLAREA system table. V$SQLAREA… Read More »