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Data, Databases, Cloud, Hadoop.
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    For a "bottom up" look of using linux OS level tools for peeking into the application performance, I'd read everything that Brendan Gregg has written (using perf or perf off-cpu events etc) http://www.brendangregg.com/linuxperf.html But, your scenario may require some application level tracing & troubleshooting too .. as the OS doesn't necessarily see the reasons of *why* some thread has chosen to go to sleep or which application level lock it is waiting for.

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    […] Tanel´s heapdump_analyzer, I could verify that the largest chunk for sga heap(3,0) was indeed 3792 bytes and that all bigger […]

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    Fixed. Thanks Tim!

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    […] After migration from 11.2.0.4. to 12.1.0.2 I discovered an interesting thing. I’ve read a lot about the new features and I was particularly interested in the Scalar Subquery Unnesting transformation. After a few tests, however, I found something that I hadn’t really expected I don’t want to explain how this transformation works because these guys did it better than I would ever do…: Jonathan Lewis Tanel Poder […]

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    […] few blog posts that explain how Oracle SQL_ID and HASH_VALUE are calculated by database engine, briefly and in detail; also implementations in Python and PL/SQL to compute […]

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    […] are various ways of avoiding this, including this, Generating lots of rows using connect by – safely!, which suggests cross-joining as many tree-walk subqueries as are necessary to generate the overall […]

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    I am stumped as to why the second half of this union gives me an error: select date '2016-10-01' from dual union all select date to_char(2016)||'-10-01' from dual; The output, if you remove the word "date" from both sides, is identical, but Oracle (12.1) can't seem to process the concatenated version.

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    Thank you for sharing this post.

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    […] “SQL*Net more data to client”, And old but still very valuable one being the one from Tanel Poder. Still I will add one – hoping to give some additional insight from a system perspective, […]

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    The DATE'xxxx' syntax is meant for a specific ANSI literal syntax, so it expects a single string constant in YYYY-MM-DD format and doesn't support complex constructs like the TO_CHAR one you used. Similarly DATE:some_bind_variable doesn't work. This is not really a UNION ALL problem, this syntax alone doesn't work either: select date to_char(2016)||'-10-01' This approach below would work if you need UNION ALL (but it uses TO_DATE): 1 select date '2016-10-01' 2 from dual 3 union all 4 select to_date(to_char(2016)||'-10-01') 5* from dual SQL> / DATE'2016-10-01' ------------------- 2016-10-01 00:00:00 2016-10-01 00:00:00