Over the years I’ve heard and learned quite a lot about how Oracle does stuff. Some of it was logical, some just details to remember (I have a really lousy memory, but somehow, I actually remember some of the details). Not too long ago I wrote a query and got a parse error, and that lead me to write this post (and a couple more that will follow).
Lately I ran into a case of losing of a voting disk, so this lead me to create a GI environment on my laptop (using virtual box) and play with voting disks failures. In this post I’ll explain what I did and what happened.
I’ve written a few “diagnostics” posts in the past (you can see them all under the “Troubleshooting” category). People really like these type of posts, and I got many comments about them in the past (good ones…), so here is another case that I had not too long ago.
I’d like to thank Kadhir Velavan, he is the guy who brought this to my attention and we worked on this issue together.
The internet is full of information about indexes, and for a reason. Indexes in a database is probably the most important performance related topic. There are so many cases, properties, and different ways to use indexes that there is simply a lot to write about. In this post I’d like to talk about a specific use case that I’ve seen a few times, and is related to index scans and performance.
Lately I had a weird problem with one of my customers regarding timezone in the database. They copied a database server from US (eastern time zone) to Europe (GMT) and changed all the OS setting to the new timezone. The application uses “sysdate” to insert data to the database, and they saw that the sysdate returns the wrong time. When I checked that, it seemed that when we used sqlplus locally on the server everything worked perfectly, sysdate, current_timestamp and systimestamp all returned the correct times with GMT. In SQL developer, however, even when running from the same timezone (GMT) the result of sysdate and systimestamp were still eastern time and not the GMT (current_timestamp returned the correct time).
Being in North America (the English speaking side), made me understand that many people are not aware (and don’t actually care) about character sets too much. Everything supports English, and everything works. Coming from Israel, I realized that some of the language issues we have in computerized systems are less understood in the western world. For example, we write from right to left (we are not the only ones, Arabic is the same for example), and I always get strange looks when I sign a piece of paper. Another example is the completely different letters (unlike English and most European languages), and more. But we are not the only ones, many countries must have these difficulties, so I decided to write this post.