SQL Server 2016, upgrading to compatability level 130,Trace flag 139 and additional one-off dbcc checks.

https://support.microsoft.com/en-gb/help/4010261/sql-server-2016-improvements-in-handling-some-data-types-and-uncommon-

When upgrading to SQL Server 2016 RTM CU3/SP1 and upgrading to database compatablity leve 130 there are additional DBCC checks which should be performed.

These are hidden behind Trace flag 139 which should be temporarily enabled as part of the process of changing database compability level to 130.

  • Enable trace flag 139 by running DBCC TRACEON(139, -1).
  • Run DBCC CHECKDB/TABLE..WITH EXTENDED_LOGICAL_CHECKS to validate persisted structures
  • Run DBCC CHECKCONSTRAINTS commands (if rows are affected the associated where clause to identify the row will be returned).
  • Disable trace flag 139 by running DBCC TRACEOFF(139, -1)
  • Change the database compatibility level to 130.
  • REBUILD any structures that you identified in step 1.

There are impovements to expression evaluation in database level 130 and this affects persisted structures

  • Check constraints
  • Persisted Computed columns
  • Indexes using computing columns whether as part of the key or as included columns
  • Filtered indexes
  • Indexed views

Upgrade to compatability level 130 BEFORE attempting to fix issues so the new expression evaluation logic is used for the fixed.

  • Check constraints – change data or drop/recreate constraint with new expression
  • Persisted Computed columns – Update a column referenced by the computed column to the same value to force recalcuation of the computed column
  • Index/filtered index/indexed views – Either A) Put db in single user mode and run DBCC CHECKTABLE with REPAIR_REBUILD B) ALTER INDEX…REBUILD and if supported in your edition of sql server consider adding the WITH (ONLINE=ON) clause.

NOTE: There are some queries in the Appendix C/D of the article above which can be used to help identify affected objects.


London BI/SQL Server user groups.

If you are BI based and want to meetup with other in London, whether technical or business based here as some contacts.

https://sqlserverfaq.com/ – General sql server (covers lots of usergroups)

http://sqllondon.pass.org/ – London SQL Pass Chapter for SQL Server but BI people do attend as well.

https://www.meetup.com/London-PUG/ London Power BI Users Group – they meet at Skills Matter, 10 South Place near Moorgate tube, big group, lots of people attend – 50+,

https://www.meetup.com/London-Business-Analytics-Group/ – London Business Analytics Group – Very power user/Business based, less technical


DB2 LUW Setting up Shadow Tables

Just heard someone at IDUG EMEA 2016 asking about how to setup DB2 LUW shadow tables.

This will depend upon DB2 Version,you also need a compatible CDC (Infosphere Replication) version,check via Finding System Requirements for IBM Software Products.

The steps are at http://www.smooth1.co.uk/db2/cancun.html#1.1

NOTE: This was written when the feature first came out DB2 LUW 10.5 FP4.

CDC Components to download were:

  • InfoSphere CDC for DB2 for LUW
  • InfoSphere CDC Access Server
  • InfoSphere CDC Management Console

Finding System Requirements for IBM Software Products.

IBM has a  Software Product Compatibility Reports facility.

http://www-969.ibm.com/software/reports/compatibility/clarity/softwareReqsForProduct.html


SQL Server on Linux notes from PASS Summit 2016

SQL Server on Linux notes from PASS Summit 2016

http://www.smooth1.co.uk/mssql/pass_summit_2016/sqlserveronlinux/SQLServerLinuxv1.htm


SSMS Running remotely

To run SSMS remotely:

runas /netonly /user:domain\username “C:\Program Files (x86)\Microsoft SQL Server\130\Tools\Binn\ManagementStudio\Ssms.exe”

E.g.

runas /netonly /user:WIN-P9OQ9GF24HV\justdave “C:\Program Files (x86)\Microsoft SQL Server\130\Tools\Binn\ManagementStudio\Ssms.exe”


SQL1227N during replaying db2look -m output

 

http://www-01.ibm.com/support/docview.wss?uid=swg21991415

db2look -m -r

The “-r” option is used to generate db2look output without runstats command output. However, current db2look code cannot reset SYSSTAT.COLUMNS and SYSSTAT.INDEXES when -r is applied. As a result, SQL1227N sometimes occur when applying the mimic when COLCARD etc, and CARD for the table is inconsistent. In db2look up to version in V10.5 please use db2look -m without -r option or insert resetting SYSSTAT.COLUMNS and SYSSTAT.INDEXES manually in db2look output with “-m” and “-r”. This limitation will be changed in releases later than V10.5. In most cases it should not cause SQL1227N error, but still the error can occur when the statistics on the source system is inconsistent. Here are examples:
Why COLCARD is sometimes bigger than CARD after RUNSTATS?
http://www.ibm.com/support/docview.wss?uid=swg21985376

Runstats may update unexpected HIGH2KEY and LOW2KEY statistic values which may cause SQL1227N
http://www.ibm.com/support/docview.wss?uid=swg21979066

As documented in above technotes, you can bypass the error by setting following undocumented registry variable even if the statistics are inconsistent:

db2set DB2_STATISTICS=USCC:0
recycle the instance

This registry variable can be used from 9.7FP9/10.1FP4/10.5.