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Parse Calls

When dealing with the library cache / shared pool it’s always worth checking from time to time to see if a new version of Oracle has changed any of the statistics you rely on as indicators of potential problems. Today is also (coincidentally) a day when comments about “parses” and “parse calls” entered my field of vision from two different directions. I’ve tweeted out references to a couple of quirkly little posts I did some years ago about counting parse calls and what a parse call may entail, but I thought I’d finish the day off with a little demo of what the session cursor cache does for you when your client code issues parse calls.

You should set OCSID.CLIENTID

each time you grab an Oracle JDBC connection from the pool

For troubleshooting and monitoring performance, you want to follow what happens from the end-user to the database. It is then mandatory to identify the end-user and application from the database session. With Oracle there are some ‘dbms_application_info’ strings to be set, like MODULE, ACTION and CLIENT_INFO. That’s about the tasks in the application code (like identifying the Java class or method from which the SQL statement is prepared) but that’s not about the end-user.

In-table predicates

This note was prompted by a recent email asking about the optimizer’s method for estimating the selectivity of a predicate which compared two columns in the same table – for example:  “where orders.amount_invoiced = orders.amount_paid”. It’s been about 14 years since I wrote “Cost Based Oracle – Fundamentals” so my memory of what I wrote (and whether I even mentioned this case) was rather hazy, so I sent off a quick reply and decided to do a little checking.

Ansible tips’n’tricks: provision multiple machines in parallel with Vagrant and Ansible

Vagrant is a great tool that I’m regularly using for building playground environments on my laptop. I recently came across a slight inconvenience with Vagrant’s Virtualbox provider: occasionally I would like to spin up a Data Guard environment and provision both VMs in parallel to save time. Sadly you can’t bring up multiple machines in parallel using the VirtualBox provisioner according to the documentation . This was true as of April 11 2019 and might change in the future, so keep an eye out on the reference.

I very much prefer to save time by doing things in parallel, and so I started digging around how I could achieve this goal.

SSIS vs. Oracle GG

This is the third in a series of product identifications between Oracle and Microsoft to assist those attempting to understand the similarities and differences between these essential parts of any data platform environments.

In this post, I’m going to describe the similarities and differences between Microsoft SQL Server Integration Services and Oracle Golden Gate. Hang on, it’s a bit of a bumpy ride. as neither service is out there on its own, (other’s piggy back off of them) and there’s definitely some new products on the Microsoft side that aren’t taken into consideration.

Describe Upgrade

Here’s an odd little change between Oracle versions that could have a stunning impact on the application performance if the thing that generates your client code happens to use an unlucky selection of constructs.  It’s possible to demonstrate the effect remarkably easily – you just have to describe a table, doing it lots of times to make it easy to see what’s happening.

19c EM Express (aka Oracle Cloud Database Express)

Oracle has a long history of interactive tools for DBA and, as usual, the name has changed at each evolution for marketing reasons.

OEM in Oracle7 #nostalgia

SQL*DBA had a Menu mode for text terminals. You may also remember DBA Studio. Then called Oracle Enterprise Manager with its SYSMAN repository and also referred to as OEM or EM. The per-database version has been called OEM “Database Control” and then “EM Express” in 12c. The multi-database version has been called according to the marketing tag “Grid Control” in 11g, and “Cloud Control” in 12c.

19c EZCONNECT and Wallet (Easy Connect and External Password File)

I like EZCONNECT because it is simple when we know the host:port, and I like External Password Files because I hate to see passwords in clear text. But the combination of the two was not easy before 19c.

Of course, you can add a wallet entry for an EZCONNECT connection string, like ‘//localhost/PDB1’ but in the wallet, you need a different connection string for each user because it associates a user and password to a service name. And you have multiple users connecting to a service.

Here is an example. I have a user DEMO with password MyDemoP455w0rd:

Oracle RAC vs. SQL Server AG

As I have seen the benefit for having a post on Oracle database vs. SQL Server architecture, let’s move onto the next frontier- High Availability…or what people think is high availability architecture in the two platforms.

To RAC or Not to RAC

There is a constant rumble among Oracle DBAs- either all-in for Oracle Real Application Cluster, (RAC) or a desire to use it for the tool it was technically intended for. Oracle RAC can be very enticing- complex and feature rich, its the standard for engineered systems, such as Oracle Exadata and even the Oracle Data Appliance, (ODA). Newer implementation features, such as Oracle RAC One-Node offered even greater flexibility in the design of Oracle environments, but we need to also discuss what it isn’t- Oracle RAC is not a Disaster Recovery solution.

Stats advisor

This is just a little shout-out about the Stats Advisor – if you decide to give it a go, what sort of things is it likely to tell you. The answer is in a dynamic performance view called v$stats_advisor_rules – which I’ve list below from an instance running 18.3.0.0.