Fixing Page Life Expectancy Steve Hood Blog: SimpleSQLServer.com

What is PLE? Duration in seconds data stays in memory References Monitor PLE in OS Perf CountersPLE in OS Perf Counters

It’s just a counter May always be low on OLAP environments Are you waiting on PAGEIOLATCH_SH? Monitor your Wait Stats Faster disks can help compensate References Monitor your Wait StatsWait Stats

Ideal Value Common advice of PLE > 300 is outdated Cache Size In GB / 4 * 300 Best generic formula References Jonathan Kehayias discusses the plan cache and PLEdiscusses the plan cache and PLE Comment discussion with Brent Ozar is as good at the article Jonathan Kehayias’s free book: Troubleshooting SQL ServerTroubleshooting SQL Server

Increase PLE More memory Query Tuning Query Justification Indexing Changes Data Cleanup

More Memory 64 GB in 2008 and 2012 Standard 128 GB in 2014 Standard Unlimited in Enterprise 768 GB is reasonable per physical box

What DBs are in cache? References Script: CacheSizeByDB

What Indexes are in Cache? References Script: CacheSizeByIndex (in speaker notes)

Finding Queries to Tune Look in the Proc Cache (not 100% reliable) Most Expensive Queries Index Usage in Proc Cache Server-Side Trace or Extended Events

Proc Cache Limitations Data since last compile Can monitor it better than that Only cacheable plans

Most Expensive Queries Uses Proc Cache For PLE focus on Physical Reads References Query Stats Monitoring – know your stats beyond your current cache Query Stats Monitoring Script: Most Expensive Queries (in speaker notes)

Index Usage in Proc Cache Uses Proc Cache Goes along with “What indexes are in cache” Gives Estimated IO cost Gives Seek and Scan Predicates References Script: Index Usage in Proc Cache (in speaker notes) Script: Table Usage in Proc Cache (in speaker notes)

Server-Side Trace or EE Duration over X seconds (5) Reads over X (100,000) References Tracing Introduction – Creating your first Server-Side Trace Tracing Introduction Reading Traces – Querying your Server-Side Trace Reading Traces Erin Stellato Making the Leap from Profiler to Extended EventsMaking the Leap from Profiler to Extended Events

How To Tune Beyond the scope of this presentation Execution Plans – Grant Fritchey Execution Plans Google SARGability BrentOzar.com SQLskills.com

Appropriate Queries? Did this query need to run? …in prod? …during peak hours?

Indexes – Drop Unused Data modifications pull data into cache Index maintenance pulls data into cache References Indexes – Unused and Duplicated

Indexes – Remove Dupes First couple key fields match Two indexes that could almost replace each other References Indexes – Unused and Duplicated

Indexes – Compression Enterprise only Some don’t compress at all Some compress by 90%

Data Cleanup Any data has potential to use cache If you can purge 25% of your data…

Fixing Page Life Expectancy Steve Hood Blog: SimpleSQLServer.com