RE: oracle v SS
- From: Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>
- To: Kellyn Pot'Vin-Gorman <dbakevlar@xxxxxxxxx>
- Date: Fri, 8 Nov 2019 08:12:12 +0000
Hi Kellyn,
I embedded my answers below.
- Another suspicious default in SQL Server is "clustered index" (as opposed to
heap table) as a data storage structure, which is similar to index organized
table (IOT) in Oracle, just the IOTs performs much better because of the
smarter implementation.
SQL Server architecture is different. Clustered indexes perform very
efficiently vs. an IOT in Oracle, which has a very unique use case, but there
is also less need for memory in the TempDB for sorting due to this design,
(no PGA, either). Keep in mind, it's again not an apple to apple comparison
when you only take the index structure into consideration.
The access over a secondary index requires an additional clustered index lookup
for getting a row. Consequently, if the clustered index depth is, say, four,
this will require four additional logical reads per fetched row. To do justice
to SQL Server, the clustered index lookup could be avoided by including all of
the selected columns in the secondary index. However, this might become quite a
challenging task in a DWH allowing ad-hoc queries. In contrast, Oracle tries to
maintain ROWIDs in the secondary index, and therefore, doesn’t require those
additional reads. I elaborated on that topic here:
https://nenadnoveljic.com/blog/index-organized-table-vs-clustered-index/ ;.
- Oracle/Linux troubleshooting/performance tuning features are superior! SQL
Server is slowly catching up, but it's still way beyond Oracle.
SQL Server is on Linux, which offers similar optimization tool availability.
Unlike Oracle, SQL Server isn’t specifically compiled for Linux. There is a
translation layer instead, see
https://cloudblogs.microsoft.com/sqlserver/2016/12/16/sql-server-on-linux-how-introduction/
. Consequently, the tools tracing user space calls can’t resolve addresses of
SQL Server functions – which renders them unusable. For example, see a
(cryptic) pstack output of a SQL Server process, which isn’t helpful at all:
pstack 1095
Thread 2 (Thread 0x7fe874b9f700 (LWP 2557)):
#0 0x00007fe87ef5dcef in ppoll () from /lib64/libc.so.6
#1 0x00005583a0cf7d41 in ?? ()
#2 0x00007fe881b46ea5 in start_thread () from /lib64/libpthread.so.0
#3 0x00007fe87ef688cd in clone () from /lib64/libc.so.6
Thread 1 (Thread 0x7fe881f5e0c0 (LWP 1095)):
#0 0x00007fe881b4e1d9 in waitpid () from /lib64/libpthread.so.0
#1 0x00005583a0cf8373 in ?? ()
#2 0x00005583a0d4c955 in ?? ()
#3 0x00005583a0d4d61f in ?? ()
#4 0x00005583a0d23eb1 in ?? ()
#5 0x00005583a0ce27df in ?? ()
#6 0x00007fe87ee8c545 in __libc_start_main () from /lib64/libc.so.6
#7 0x00005583a0cdfbba in ?? ()
In contrast, pstack output of an Oracle process provides a genuinely useful
information:
pstack 29069
#0 0x00007f627002015a in semtimedop () from /lib64/libc.so.6
#1 0x0000000012840365 in sskgpwwait ()
#2 0x000000001283c4bb in skgpwwait ()
#3 0x0000000012034d9a in ksliwat ()
#4 0x000000001203414c in kslwaitctx ()
#5 0x0000000012657e20 in ksarcv ()
#6 0x0000000003a2837a in ksbabs ()
#7 0x0000000003a46933 in ksbrdp ()
#8 0x0000000003e2a8cd in opirip ()
#9 0x00000000026d3265 in opidrv ()
#10 0x0000000003185685 in sou2o ()
#11 0x0000000000da9f1d in opimai_real ()
#12 0x0000000003191821 in ssthrdmain ()
#13 0x0000000000da9e40 in main ()
- SQL Server comes with BI components (Reporting & Analysis Server, SSIS).
Most newer, advanced, more efficient products are not in SQL Server, but
Azure DB and Azure in general. Power BI, Analysis Server, Hyperscale, Azure
Data Factory). It may be less popular in the Oracle world, but I'm at one of
the largest Microsoft conferences today and I can tell you, most of us have
moved to the cloud and cloud products. SQL Server outside of Azure is when
we have no other choice. There's so much more available in Azure.
According to
https://docs.microsoft.com/en-us/power-bi/report-server/install-report-server , ;
Power BI is available on-premise as well.
Best regards,
Nenad
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