Category Archives: Databases

#Oracle: ORA-02298: cannot validate "key" – parent keys not found

By | December 17, 2019

When trying to add a foreign key to a table sometimes the error ORA-02298 is thrown. Let’s have two tables a MyTable and a MyTableHistory connected by a historyid column from MyTable that points to the id column from MyTableHistory Try then to add add foreign key like: If we are in the case of… Read More »

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Migrating a #PostgreSQL database to a diferent PostgreSQL version or to a restrictive Postgres instance of cloud providers like #AWS-RDS

By | December 11, 2019

There are instances when one needs to migrate data from a Postgres database to a different PostgreSQL database version or even worse to a restrictive PostgreSQL instance of cloud providers like #AWS-RDS. When migrating to a different version of Postgres after you used to run on a frozen production version for long time it may… Read More »

Migrate legacy application using Oracle 10g to Oracle 12c

By | March 16, 2019

After upgrading my developement Oracle database to 12c I discovered that an old legacy application still under support was no longer working throwing the following Oracle error: After some digging I found the following reported bug: Bug 14575666 In 12.1, the default value for the SQLNET.ALLOWED_LOGON_VERSION parameter has been updated to 11. This means that… Read More »

Investigate #Oracle #deadlocks

By | May 10, 2018

Sometimes we may end up having some application resources competing for the same resource on our Oracle database. This is usually the case when some exclusive resource must be allocated or updated as in the case of database based locking mechanisms. If there are code issues we may end up in a deadlock situation when… Read More »