PI System Management Best Practices

Bryan S. Owen P.E.OSIsoft Field Service

Focus on BenefitsImprove

SustainAssess

Change Management Interacts with System Management!

Change Management and Continuous Improvement

Typical PI Improvement Projects• Server Upgrades• Custom Applications• Raw Data Collection• Performance Calculations• Layered Data Structures• Desktop Deployments• Skill Development

PI Server Upgrade

Stage Upgrade on Spare Platform• Preferred O/S – Windows 2K

• Windows Domain Membership

• Test with PItoPI or Parallel Interfaces

Review PI Timeout Table• Maxupdatequeue, Totalupdatequeue, Readtimeout

• http://support.osisoft.com/FieldService/service_downloads.htm

Interface Status Watchdog (Optional)• “flatline” detection

• optional status change for input points

Custom Application Guidelines

Preferred Core PI Technology• SQL (OLEDB Provider)• OPC Server• SDK/API

Deployment Hints• Dedicated PI User Name• Identify all Inputs and Outputs to PI• Assign DataOwner on Output Points

RtPM Pyramid

Data Collection from Inside and Outside the Corporation

Execs Look for Equipment, Plants, Products, not Tags

Aggregation, Reconciliation, Calculation, Cases

Get the Information to People Who Need It

People Need Pictures, Graphs, Trends

Without Action, there is no Benefit

Gather

Assign Context

Analyze

Distribute

Visualize

Act

Connectors or Interfaces?

Integrated Data Source• Archive is provided

by source system• No data replication • PI queries redirected

to source host

Constraints: scalability, connection latency

Hot: OLEDB Connector

Decoupled Data Source• No archive retention

burden on source host• Scheduled replication• PI queries resolved

locally

Constraints: scan rate and out of order data

Hot: OPC Interface

Data Source Reconciliation

Periodic Discovery• Automatic Point Synchronization

(yes, OPC connector!)• Dedicated workstation is suggested

Point Deletion• Server concordance check

(SMT advanced search…getpointssql)• Alternative: set ptaccess=“o: g: w:”

Point Type Selection…Float16 vs Float32

FLOAT32 is easy on the administrator but…• No under/over range sanity check

(unless a supported by the interface).

• Dirty zero affects aggregates differently(not reflected in percent good, use Totalizer with zerobias).

• Performance penalty (~2x archive i/o).

FLOAT16 rules of thumb…• Well defined zero and span required.• Large scale systems >50,000 pts.• Sub second data collection.• High data density applications (PI profile points).

Interface Accuracy

Scan Class Schedules• Avoid schedule collisions

Dedicated Instances• Load balancing and isolation• Event triggers and outputs• Special handling

(stopstat, watchdog list)

Report all changes to PI• Minimize Excdev (zero is ok!)• Buffer recovery is constraint

Compression Guideline

Ideal: set based on process specification• usually <1% compression deviation

Easy: use rated instrument precision• Excess archiving is a potential process

issue or sampling limitation.• If possible, resolve “noise” at the source

(filter may be an appropriate remedy).

RtPM Pyramid

Data Collection from Inside and Outside the Corporation

Execs Look for Equipment, Plants, Products, not Tags

Aggregation, Reconciliation, Calculation, Cases

Get the Information to People Who Need It

People Need Pictures, Graphs, Trends

Without Action, there is no Benefit

Gather

Assign Context

Analyze

Distribute

Visualize

Act

Layered Data Structures in PI

Base• Digital Sets• Headings• Aliases• Properties• Modules

Archive• Batch, UnitBatch/SubBatch, Transfers

Digital Sets

System set is global• Applies to all points• Important factory defaults include

• “Shutdown”, “Intf Shut”, “I/O Timeout”

Digital points preferred over string tags• Enables multistate symbols and trends• Create dedicated state sets• Include placeholders for volatile sets

PI Headings…mutant Digital Sets!

• Name, Level and Description• Level starts at 1• Discontinuous sequences ok• Optional Module or SubBatch property

PI Alias Collections…Cached point lists

• Organize points by module• Leverage utility with alias names• Multiple aliases for the same tag ok• Join tags from any number of servers

Alias “aware” applications:• ACE, Batchview, MDB Editor• OLEdb Provider, OPC Server, SDK/API

PI Property Collections…Named Value Tables

Collections in free format hierarchal structures.

Associate nominally “static” properties with a Module.

Stored in Archive when assigned to a Batch or Transfer Record.

PI Module Collections…File System for PI

Free format hierarchy, a PI module may “link” to multiple collections.

Access rights depend on DBsecurity and the root module owner.

Versioning and query control based on “effective” date.

“isPIunit” creates archive point for unitbatch recording.

Layered Data Structures in PI…Management Tips

Restrict write access (DBsecurity default)• Digital Sets – PIDS• ModuleDB – PIModules, PIHeadingSets

Standardize Digital Sets across an Enterprise• Especially useful with PItoPI implementation

Configure ModuleDB with SDK/VB scripts:• Transmission Line Demo

RtPM Pyramid

Data Collection from Inside and Outside the Corporation

Execs Look for Equipment, Plants, Products, not Tags

Aggregation, Reconciliation, Calculation, Cases

Get the Information to People Who Need It

People Need Pictures, Graphs, Trends

Without Action, there is no Benefit

Gather

Assign Context

Analyze

Distribute

Visualize

Act

Server CalculationsPerformance Equation StudyOver 15 servers & 5500 expressions

• …expression lengthMedian 50 characters, 95% < 162, Max=2851!

• …archive function calls (~10% of total )Median time span <9 hrs, Max since 1970!

• …nesting levels (excluding circular logic)One Level 25%, Two Levels 9%, More 2.5%

• …variables per expression (max=156!)

Performance Equation Study…Conclusions

Primary Usage Analysis• simple transformations…y=mx+b, steam tables• data smoothing…tagavg, medianfilt• state detection / signal selector…if then else

Conclusions• 80% of PE expressions are appropriate• 20% in need of redesign

• Implement in ALARM or TOTAL processor• Logic or schedule more appropriate for ACE

Performance Equation Tips

Develop Expressions on PI Desktop• Datalink “Expression Calculation”• Processbook “PI Dataset”

Don’t implement on production servers until proven!

Scheduling Options• Run simple transforms at raw scan rate• Uniint event triggers

Event=‘motorstatus’ increment, (run on 0 -> 1 transition)

• Enable Recalc for expressions with LAB inputs

RtPM Pyramid

Data Collection from Inside and Outside the Corporation

Execs Look for Equipment, Plants, Products, not Tags

Aggregation, Reconciliation, Calculation, Cases

Get the Information to People Who Need It

People Need Pictures, Graphs, Trends

Without Action, there is no Benefit

Gather

Assign Context

Analyze

Distribute

Visualize

Act