Tag: Technical Blog

Database Upgrade Fails With “unexpected error in validate_credentials”

unexpected error

This is a blog post about an issue that can occur during a database upgrade and produces a misleading error message. If you’re already aware of it, the workaround is trivial. However, when it happened to me during the testing…

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Statspack vs. AWR: Wrong number of SQL Executions

oracle

This post is about a Statspack anomaly I discovered while analyzing execution trends of a particular SQL on one of our clients’ databases. I decided to share it, since its appearance can be misleading. The database in question was an…

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Part Four: Deploying High Availability Applications in Oracle Cloud Infrastructure—Oracle Enterprise Manager 13.5 Setup

oraclecloud

This is the fourth in a series of blog posts that covers the details to deploy a high available set up of Oracle Enterprise Manager 13.5 using Oracle Cloud Infrastructure’s resources.   Recap This is the fourth of a six-part…

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Python: Using Dataclasses to Model Your Data

3d chart data model tablet

Here at Pythian, we love our data. Our code is no exception (pun sort of intended), so I’ll be covering dataclasses in Python today. The problem As a Python developer, you’ve almost certainly run into code that looks like the…

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Mitigating the Problems Created by Tombstones

Got too many tombstones? This blog post will talk about how to deal with tombstones once you already have them. For more information about tombstones, check out this post: Examining the Lifecycle of Tombstones in Apache Cassandra. Verifying the presence…

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Consuming Tweets Using Apache Beam on Dataflow

Apache Beam is an SDK (software development kit) available for Java, Python, and Go that allows for a streamlined ETL programming experience for both batch and streaming jobs. It’s the SDK that GCP Dataflow jobs use and it comes with…

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DML by Unique Index Supposedly Affecting Many Rows

This blog post is based on a real customer case, and illustrates how v$sql reports execution statistics for certain DML types of operations (I purposely have not named which DML types … yet). These reports can be misleading when troubleshooting…

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Issues With Database Service Names Starting With Pluggable Database (PDB) Name

In this post I’ll describe a problem which occurs when creating and using a database service name which starts with the pluggable database’s (PDB) name, and has a dot (“.”) after it: “<pdb_name>.<optional_suffix>.” I noticed this issue when I was…

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Query Statspack’s “SQL ordered by” Sections Over a Time Period

In this post, I’ll present the statspack_top_sqls.sql script, which returns SQL performance statistics by mining the Statspack repository. In a previous blog post, I presented the statspack_load_trends.sql and the AWR_load_trends.sql scripts, which provide a high-level overview of workload dynamics on…

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Mining Statspack and AWR Repositories for Historical Trends

There are various ways that we can approach the analysis of a past database performance problem. The initial steps usually differ based on their scope. Is it limited to a certain SQL/process/task, or is it perceived as a database-wide slowdown?…

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