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Category: Administration

Threads Need Memory Too

Arun Sirpal notices a bug with fn_dump_dblog():

Using this command creates more threads and hidden schedulers (these will only go after a restart). Depending on what version of SQL Server you are on and what Service Pack you may or may not have this issue. It was fixed in SQL 2012 SP2 onwards. So be on the cautious side when running these sorts of commands.

Also I noticed Memory bloat for the sqlservr.exe. Nothing else was running on this server, just my fn_dump_dblog script.  Threads need memory too.

It’s good advice.  Undocumented functions are probably more likely than documented functions to contain bugs.

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SSISDB Maintenance

Jesse Seymour shows how to trim the SSIS catalog size:

The options we are interested in are OPERATION_CLEANUP_ENABLED and RETENTION_WINDOW.  By default, RETENTION_WINDOW is 365. and OPERATION_CLEANUP_ENABLED is TRUE.

Since we want to set our retention window to 10 days, we need to update RETENTION_WINDOW to 10.  We could do this with a simple update statement, but Microsoft provides us with a stored procedure that will do that for us.  The benefit of the stored procedure over the UPDATE statement is that a vendor-provided stored procedure will typically encapsulate any additional steps required.

I do not at all like the idea of running SHRINKDATABASE and definitely wouldn’t have that plus a backup in the deletion loop, but if you get caught in a nasty situation with SSISDB, this can serve as the starting point for digging yourself out.

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Linked Server To Access

Jana Sattainathan walks through issues with setting up a linked server connection to an Access database:

Normally, it is easy enough to setup a Linked Server on SQL Server to other data sources. Problems are usually caused by one of the usual culprits that have to be addressed

  • SQL Logins simply do not work well when trying to do this type of setup

  • The Windows login has to have permissions to the file (on a drive or network share)

  • The appropriate drivers have to be setup (64 bit / 32 bit)

Read on for a few different errors and their solutions.

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Syncing Logins Between AG Replicas

Daniel Hutmacher has a new series on Availability Group synchronization, starting with logins:

You’ll need a linked server from your secondary replica to the primary replica. This linked server should feature the absolute bare-minimum of permissions, preferably with only the “be made using the login’s current security context” selected.

The account running the procedure (or the mapped login in the linked server) will need SELECT access to the following DMVs on the remote (primary) server:

  • master.sys.server_principals

  • master.sys.sql_logins

  • master.sys.server_role_members

  • master.sys.server_permissions

The code itself is a download from Daniel’s website; go check it out.

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Attaching Databases With CDC Enabled

Amit Banerjee notes an issue with detaching a database with Change Data Capture enabled and moving it to a new version of SQL Server:

When you detach a database with Change Data Capture enabled on SQL Server 2014 and below and attach it to a SQL Server 2016 instance, you could run into the error mentioned below while execute Change Data Capture (CDC) related procedures.

Error:

Msg 22832, Level 16, State 1, Procedure sp_cdc_enable_table_internal, Line 639 [Batch Start Line 0]

Could not update the metadata that indicates table [<schema name>].[<object name>] is enabled for Change Data Capture. The failure occurred when executing the command ‘insert into [cdc].[captured_columns]’. The error returned was 213: ‘Column name or number of supplied values does not match table definition.’. Use the action and error to determine the cause of the failure and resubmit the request.

Read on to learn more, including how to fix the issue.

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Test Restores

Steve Jones implores you to test those database backups by restoring them somewhere:

What do you do? Hopefully you recognize the issue and can fix the issue. Maybe more importantly, you have a backup of the missing certificate.

Most people don’t deal with encryption, but you never know when your backup job might start failing, perhaps writing to a damaged file that appears to work (if you write as a device) but really isn’t capturing the backup file. Perhaps you don’t know that your backups are being written to a location and deleted a day later, but the process that is supposed to copy them to tape or a remote file share is broken.

Any number of things can happen. The point is that you want to be sure that you are actually getting useable backup files.

That means testing restores.

Read the whole thing.

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CAP_CPU_PERCENT

Robert Davis looks at the CAP_CPU_PERCENT option in Resource Governor:

The need for this setting came about because MAX_CPU_PERCENT is not applied unless the server is busy. This could lead to a situation where queries in a low priority resource pool starts running while the server is idle and are allowed to consume all the CPU they can. Then high priority queries spin up, and they can’t immediately get the CPU they need due to the low priority queries not being capped. CAP_CPU_PERCENT came along and was designed to set a hard limit that the queries in a pool could not go over even if the server is idle. For example, if you cap the CPU at 25%, the queries in the pool will not exceed 25% no matter how idle the server is.

Problem solved, right?

When the end of a section is a yes/no question, the answer is usually “no.”  Read on before this burns you.

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Nothing New Under The Sun

Kevin Hill reminisces and warns:

Installation defaults that are going to bite you (not version specific, and the installer is getting better):

  • Files all on the C drive

  • One TempDB data file (improved in SQL 2016)

  • Backups on C drive

  • No automated backups

  • Allow SQL to use ALL the memory

  • Allow SQL to use ALL the CPUs

  • Builtin\Administrators group not default*

  • Compressed backup set to OFF

There’s good advice here, so read on.

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Who Monitors The Monitors?

Dave Mason discusses monitors and what happens when they fail:

I was reminded of this recently in my little SQL Server world. I have a number of garden variety alerts set up, plus some other more custom monitoring stuff, which is mostly tied to DDL triggers and event notifications. The one thing all of them have in common is database mail. You can probably guess where I’m going with this. Yep, database mail stopped working. A couple weeks passed before I realized it. Fortunately, out of all the alerts I should have been notified about, none of them were serious.

How would I prevent this happening in the future? I guess I could build another system to monitor my monitoring system. Something like System C, which monitors System B, which monitors System A. But where would that end? System D? System E? Where should the line be drawn? I don’t know that there’s a right answer here, although admittedly, the farther into the alphabet you get, the more absurd it sounds.

At some level, process becomes the answer.  In my case, not before I create a few more systems…

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KB2919355

Allan Hirt notes that you need KB2919355 installed before you can install SQL Server 2016 on Windows Server 2012 R2 or Windows 8.1:

In my case, I created a new VM with a fresh installation of Windows Server 2012 R2. I also ran Windows Update to ensure it had everything Windows Server thought it required. Figure 3 reflects this status.

As you can see in Figure 4, KB2919355 is not listed as one of the ones WU installed, so it has to be an optional update.

Looking at the list of optional updates in Windows Update in Figure 5, 2919355 is not shown. This means you need to download and install it manually.

It’s never quite as easy as “just run this patch,” so do read on for another gotcha.

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