enq: TX – row lock contention

I received a case where a developer had a session that hung waiting on  enq: TX – row lock contention. It was several things that puzzled me, he claims he is the only one running on this database and the row lock was related to an insert.

insert into PRODUCT (ID, VIN, CHASSISSERIES, CHASSISNO, MODIFICATIONTIME, CREATIONTIME) values (:1 , :2 , :3 , :4 , :5 , :6 )

I found this a bit odd at first. I relate enq: TX row lock contention with updates and deletes, not inserts. I want to analyze this further.

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Group Column Statistics (Part 2)

As described in Part 1 Oracle gathers extended statistics automatically on column groups. This was also available in 11g but here you had to add it manually.

How can this become a performance issue in our 12c database ? If you read my post about   our performance issues related to this you know that we spent a lot of time hard parsing and that we  saw a specific sql on the top list for parsing.

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Group column statistics (part 1)

So group column statistics, what is it ? it is information about relationship between columns in the same table. There are numerous blogs about this. One I read is the Oracle Optimizer Blog explaining the details. This is from 11g when you had to create it manually.
From it is done on the fly, which can cause issue. See my previous post about my experiences. This post is a spin off from that post explaining the details a bit more.

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Poor Performance related to ADS (Part2)

(read Part1 here)

Why do I need a part two ? well in part 1 i said  that “I’m (almost) sure we suffered from Very Long Parse Time for Queries in In-Memory Database (Doc ID 2102106.1).”
So glad I added (almost) because now it seems we still have the same issue during our last batch run. I did a few tests after setting inmemory_query=disable and it worked fine, but my testing was obviously not good enough.

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Cursors not shared due to ROLL_INVALID_MISMATCH

I frequently check my customers databases, during one of these controls I found that we had many versions of the same sqls with reason ROLL_INVALID_MISMATCH. I do not experiencing an issue around high version count. Hard parse is not an issue and shared_pool is not using a lot of memory. I just want to understand whats behind the figures. This is what I found.

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