DBA Blocking Sessions

Description:

Chain of currently blocking and blocked database sessions from v$wait_chains

Parameters

Used tables

dba_objects, v$wait_chains, gv$session, gv$process, gv$sqlarea

Dependencies

If you would like to try one of these Oracle EBS SQLs without having Blitz Report installed, note that some of the reports require functions from utility package xxen_util.

Example Report

DBA Blocking Sessions 06-May-2020 103312.xlsx

Report SQL

www.enginatics.com/reports/dba-blocking-sessions/

Blitz Report™ import options

DBA_Blocking_Sessions.xml

DBA Blocking Sessions - Case Study

Executive Summary

The DBA Blocking Sessions report is a critical diagnostic tool for Oracle E-Business Suite Database Administrators (DBAs). It provides real-time visibility into database lock contention, identifying sessions that are blocking others and causing performance degradation. By visualizing the chain of blocking and blocked sessions, DBAs can quickly pinpoint the root cause of system slowness or “hanging” processes and take immediate corrective action.

Business Challenge

In a high-concurrency environment like Oracle EBS, database locking is a normal mechanism to ensure data integrity. However, when a session holds a lock for an extended period (due to a long-running transaction, uncommitted changes, or a “zombie” process), it can prevent other users from accessing the same data. This leads to:

System Slowness: Users experience delays or unresponsive screens.
Operational Stalls: Critical business processes (e.g., order entry, month-end close) may be halted.
User Frustration: Lack of visibility into why the system is slow leads to increased helpdesk tickets.

Identifying the specific session holding the lock—and the SQL statement it is executing—is often like finding a needle in a haystack without the right tools.

Solution

The DBA Blocking Sessions report solves this challenge by querying Oracle’s v$wait_chains and related dynamic performance views. It presents a hierarchical view of the blocking chain, showing exactly which session is at the top of the chain (the “blocker”) and which sessions are waiting (the “blockees”).

Key Features:

Hierarchical View: Displays the relationship between blocking and waiting sessions.
Real-Time Analysis: Provides a snapshot of current lock contention.
Detailed Diagnostics: Includes session IDs, user names, machine names, SQL text, and wait events.
Actionable Intelligence: Enables DBAs to decide whether to contact the user, kill the session, or optimize the underlying SQL.

Technical Architecture

The report leverages Oracle’s Active Session History (ASH) and wait interface architecture.

Primary Tables/Views:

v$wait_chains: The core view for identifying blocking relationships in RAC and non-RAC environments.
gv$session: Provides details about the active sessions (User, Module, Machine, Status).
gv$process: Links sessions to operating system processes.
gv$sqlarea: Retrieves the SQL text currently being executed by the sessions.
dba_objects: Identifies the database object (table, index) involved in the lock.

Logic: The query joins v$wait_chains with session and SQL information to construct a readable output. It filters for sessions that are currently in a wait state due to another session.

Frequently Asked Questions

Q: What is the difference between a “blocking” session and a “blocked” session? A: A blocking session holds a lock on a resource (like a row in a table). A blocked session is trying to acquire a lock on the same resource but must wait until the blocking session releases it (usually by committing or rolling back).

Q: Does this report show historical blocking sessions? A: No, this report shows current blocking sessions. For historical analysis, you would typically use AWR (Automatic Workload Repository) or ASH (Active Session History) reports.

Q: What should I do if I find a blocking session? A: First, analyze the “blocker.” Is it a valid long-running job? If so, you may need to wait. Is it a user who left their screen open with uncommitted changes? You might contact them. Is it a “stuck” process? You might need to kill the session.

Q: Can this report handle RAC (Real Application Clusters) environments? A: Yes, the use of gv$ (Global) views and v$wait_chains ensures that blocking chains across different RAC nodes are detected.

Oracle E-Business Suite Reporting Library

We provide an open source Oracle EBS SQLs as a part of operational and project implementation support toolkits for rapid Excel reports generation.

Blitz Report™ is based on Oracle EBS forms technology, and hence requires minimal training. There are no data or performance limitations since the output files are created directly from the database without going through intermediate file formats such as XML.

Blitz Report can be used as BI Publisher and Oracle Discoverer replacement tool. Standard Oracle BI Publisher and Discoverer reports can also be imported into Blitz Report for immediate output to Excel. Typically, reports can be created and version tracked within hours instead of days. The concurrent request output automatically opens upon completion without the need for re-formatting.

The Filters, Columns, Rows and Values fields are used to create and deliver the data in pivot table format with full drill down to details.

Blitz Report Pivots

The Excel template upload functionality in Blitz Report allows users to create their own layouts by uploading an Excel template with additional sheets and charts, automatically refreshed when the report runs again. This allows to create custom dashboards and more advanced visualizations of report data.

Blitz Report Dashboard

You can download and use Blitz Report free of charge for your first 30 reports.

The installation and implementation process usually takes less than 1 hour; you can refer to our installation and user guides for specific details.

If you would like to optimize your Oracle EBS implementation and or operational reporting you can visit www.enginatics.com to review great ideas and example usage in blog. Or why not try for yourself in our demo environment.

Alert	CRM Foundation
ALR Alerts	JTF Grid Datasources
Contracts Core	Lease and Finance Management
OKC Contract Lines Summary	OKL Termination Quotes
Payments	Process Manufacturing Inventory
IBY Payment Process Request Details	GMI Cycle Count Forms
Public Sector Financials	Shipping Execution
PSA Budgetary Control Transactions	WSH Shipping/Delivery Transactions
Warehouse Management	XML Publisher
WMS Control Board Tasks	XDO Publisher Data Definitions
Capacity	Legal Entity Configurator
CRP Available Resources CRP Resource Plan	XLE Establishment and Legal Entity Associations XLE Legal Entities
Service Contracts	Applications DBA
OKS Service Contracts Billing History OKS Service Contracts Billing Schedule	AD Applied Patches AD Applied Patches 11i AD Applied Patches R12.2
Enterprise Asset Management	Installed Base
EAM Assets EAM Weekly Schedule EAM Work Orders	CSI Customer Products Summary CSI Installed Base Extended Attributes Summary CSI Installed Base Summary by Organization
Payroll	Process Manufacturing
PAY Costing Detail PAY Employee Payroll History PAY Payroll Element Details	OPM Batch Lot Cost Details OPM Batch Lot Cost Trends OPM Reconcilation
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XLA Distribution Links Summary XLA Entity ID Mappings XLA Subledger Period Close Exceptions	WF Activity Status Summary WF Business Events and Subscriptions WF Notifications
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PN GL Reconciliation PN Generate Lease Analysis PN Generate Lease Details PN Generate Portfolio Detail PN Generate Portfolio Summary	MSC Exceptions MSC Horizontal Plan MSC Pegging Hierarchy MSC Pegging Hierarchy 11i MSC Plan Orders MSC Vertical Plan
E-Business Tax	Projects
ZX Financial Tax Register ZX Lines Summary ZX Party Tax Profiles ZX Tax Accounts ZX Tax Regimes ZX US Sales Tax	PA Capital Project Summary with Asset Detail PA Project Budget PA Revenue, Cost, Budgets by Resources PA Revenue, Cost, Budgets by Work Breakdown Structure PA Task Schedule PA Transaction Sources
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Order Management	Work in Process
ONT Cancelled Orders ONT Order Holds ONT Orders ONT Orders and Lines ONT Recurring Billing Plan ONT System Parameters ONT Transaction Types Listing ONT Transaction Types and Line WF Processes	WIP Account Distribution WIP Discrete Job Shortage WIP Entities WIP Entities Summary WIP Outside Processing WIP Required Components WIP Value WIP Value Summary
Cash Management	Cost Management
CE Bank Account Balances CE Bank Branches CE Bank Statement Import Execution CE Bank Statement and Reconciliation CE Bank Transaction Codes Listing CE Cash in Transit CE Cleared Transactions CE General Ledger Cash Account Usage CE General Ledger Reconciliation CE Transactions Available for Reconciliation	CST AP and PO Accrual Reconciliation CST COGS Revenue Matching CST Cost Groups CST Detailed Item Cost CST Inventory Value - Multi-Organization (Element Costs) 11i CST Inventory Value - Multi-Organization (Item Costs) CST Inventory Value Report - by Subinventory (Item Cost) CST Item Cost Reports CST Miscellaneous Accrual Reconciliation CST Period Close Subinventory Value CST Period Close Subinventory Value Summary CST Periodic Inventory Value CST Supply Chain Indented Bills of Material Cost CST Uninvoiced Receipts
Purchasing	Discoverer
PO Approval Assignments PO Approval Groups PO Approved Supplier List PO Cancelled Purchase Orders PO Cancelled Requisitions PO Document Types PO Headers PO Headers 11i PO Headers and Lines PO Headers and Lines 11i PO Internal Requisitions and Sales Orders PO Internal Requisitions/Deliveries Discrepancy PO Invoice Price Variance PO Purchase Price Variance PO Purchase Requisitions with PO Details	DIS Access Privileges DIS Business Areas DIS Discoverer and Blitz Report Users DIS End User Layers DIS Folders, Business Areas, Items and LOVs DIS Import Performance DIS Items, Folders and Formulas DIS Migration identify missing EulConditions DIS Users DIS Workbook Export Script DIS Workbook Import Validation DIS Workbook Owner Export Script DIS Workbooks, Folders, Items and LOVs DIS Worksheet Execution History DIS Worksheet Execution Summary DIS Worksheet SQLs
Assets	Payables
FA Additions By Source FA Asset Additions FA Asset Book Details FA Asset Book Details 11i FA Asset Cost FA Asset Impairments FA Asset Inventory FA Asset Inventory Report FA Asset Reclassification FA Asset Register FA Asset Retirements FA Asset Summary (Germany) FA CIP Cost FA Cost Adjustments FA Depreciation Projection FA Depreciation Reserve FA Journal Entry Reserve Ledger FA Revaluation Reserve FA Tax Reserve Ledger	AP 1099 Payments AP Accounted Invoice Aging AP Cash Requirement AP DPIVA Export LSNA AP Expenses AP Final Payment Register 11i AP Intercompany Invoice Details AP Invoice Approval Status AP Invoice Audit Listing AP Invoice Payments AP Invoice Payments 11i AP Invoice on Hold AP Invoice on Hold 11i AP Invoices and Lines AP Invoices and Lines 11i AP Invoices with PO, Intercompany and SLA Details AP Matched and Modified Receipts AP Negative Supplier Balance AP Open Balances Revaluation AP Open Items Revaluation AP Posted Invoice Register AP Posted Payment Register AP Preliminary Payment Register 11i AP Supplier Statement AP Suppliers AP Suppliers 11i AP Suppliers Revenue Summary AP Suppliers Revenue Summary 11i AP Trial Balance AP Trial Balance Report Definitions
Receivables	General Ledger
AR Adjustment Register AR Aging AR Aging Buckets and Interest Tiers Setup AR Applied Receipts AR Autoinvoice Interface Summary AR Customer Credit Limits AR Customer Credit Snapshot AR Customer Open Balances Period Lookback AR Customer Statement AR Customers and Sites AR Disputed Invoice AR European Sales Listing AR Incomplete Transactions AR Miscellaneous Receipts AR Miscellaneous Receipts 11i AR Open Balances Revaluation AR Open Items Revaluation AR Past Due Invoice AR Payment Terms AR Receipt Register AR Sales Journal By Customer AR Transaction Register AR Transaction Types AR Transactions and Lines AR Transactions and Lines 11i AR Transactions and Payments AR Transactions and Payments 11i AR Unaccounted Transaction Sweep AR Unapplied Receipts Register AR to GL Reconciliation	GL Account Analysis GL Account Analysis (Distributions) GL Account Analysis (Distributions) 11g GL Account Analysis (Drilldown) GL Account Analysis (Drilldown) (with inventory and WIP) GL Account Analysis 11g GL Account Analysis 11i GL Balance GL Balance (pivot) GL Balance by Account Hierarchy GL Code Combinations GL Daily Rates GL Data Access Sets GL FSG Reports GL FSG Row Orders GL Financial Statement and Drilldown (FSG) GL Header Categories Summary GL Journals GL Journals (Drilldown) GL Journals (Drilldown) 11g GL Journals 11i GL Ledger Sets GL Ledgers and Legal Entities GL Ledgers and Organizations GL Oracle FSG Converter GL Oracle FSG Converter 11g GL Period Status GL Periods GL Summary Templates GL Trial Balance - Detail GL effective vs accounting vs period start and end date comparison
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Blitz Report Application Categories Blitz Report Assignments Blitz Report Assignments and Responsibilities Blitz Report Category Assignments Blitz Report Column Number Fomat Comparison between environments Blitz Report Column Translation Comparison between environments Blitz Report Column Translations Blitz Report Comparison between environments Blitz Report Default Templates Blitz Report Deletion History Blitz Report Execution Summary Blitz Report History Blitz Report LOV Comparison between environments Blitz Report LOV SQL Validation Blitz Report LOVs Blitz Report License User History Blitz Report License Users Blitz Report Parameter Anchor Validation Blitz Report Parameter Bind Variable Validation Blitz Report Parameter Comparison between environments Blitz Report Parameter Comparison between reports Blitz Report Parameter Custom LOV Duplication Validation Blitz Report Parameter DFF Table Validation Blitz Report Parameter Default Values Blitz Report Parameter Dependencies Blitz Report Parameter Table Alias Validation Blitz Report Parameter Uniqueness Validation Blitz Report Pivot Colums Validation Blitz Report RDF Import Validation Blitz Report Record History SQL Text Creation Blitz Report SQL Validation Blitz Report Security Blitz Report Templates Blitz Report Text Search Blitz Report Translations Blitz Report User History Blitz Report VPD Policy Setup Blitz Reports Blitz Upload Data Blitz Upload Dependencies Blitz Upload History	INV ABC assignments INV Aging INV Cycle count entries and adjustments INV Cycle count hit/miss analysis INV Cycle count listing INV Cycle count open requests listing INV Cycle count schedule requests INV Cycle count unscheduled items INV Cycle counts pending approval INV Default Category Sets INV Intercompany Invoice Reconciliation INV Intercompany Invoice Reconciliation 11i INV Item Category Assignment INV Item Category Sets INV Item Default Transaction Locators INV Item Default Transaction Subinventories INV Item Demand History INV Item Import Performance INV Item Relationships INV Item Reservations INV Item Statuses INV Item Supply/Demand INV Item Templates INV Items INV Lot Transaction Register INV Material Account Distribution Detail INV Material Movements INV Material Status Change History INV Material Transactions INV Material Transactions Summary INV Onhand Quantities INV Organization Access INV Organization Parameters INV Period Close Pending Transactions INV Physical Inventory Adjustments INV Physical Inventory Tags INV Physical inventory accuracy analysis INV Print Cycle Count Entries Open Interface data INV Safety Stocks INV Stock Locators INV Subinventories INV Transaction Historical Summary INV Transaction Register INV Transaction Source Types INV Transaction Types
Application Object Library	Database Administration
FND Application Context File FND Applications FND Attached Documents FND Attachment Functions FND Audit Setup FND Audit Table Changes by Column FND Audit Table Changes by Record FND Concurrent Managers FND Concurrent Program Incompatibilities FND Concurrent Programs and Executables FND Concurrent Programs and Executables 11i FND Concurrent Request Conflicts FND Concurrent Requests FND Concurrent Requests 11i FND Concurrent Requests Summary FND Data Groups FND Descriptive Flexfield Table Columns FND Descriptive Flexfields FND Document Categories FND Document Sequence Assignments FND Document Sequences FND FNDLOAD Object Transfer FND Flex Hierarchies (Rollup Groups) FND Flex Value Hierarchy FND Flex Value Security Rules FND Flex Value Sets, Usages and Values FND Flex Values FND Form Functions FND Forms Personalizations FND Help Documents and Targets FND Histogram Columns FND Key Flexfields FND Languages FND Lobs FND Log Messages FND Lookup Search FND Lookup Values FND Lookup Values Comparison between environments FND Menu Entries FND Messages FND Nodes FND Profile Option Values FND Profile Options FND Request Groups FND Responsibilities FND Responsibility Access FND Responsibility Access 11i FND Responsibility Menu Exclusions FND Role Hierarchy FND Roles FND Rollup Groups FND SOA Runtime Error FND Tables and Columns FND User Login History FND User Login Page Favorites FND User Login Summary FND User Responsibilities FND User Roles FND User Roles 11i FND Users	DBA AWR Active Session History DBA AWR Blocking Session Summary DBA AWR CPU Load (active session history) DBA AWR CPU vs Wait Time Summary DBA AWR Interconnect Traffic DBA AWR Latch Summary DBA AWR Latch by Time DBA AWR PGA History DBA AWR SQL Execution Plan History DBA AWR SQL Performance Summary DBA AWR Settings DBA AWR System Metrics Summary DBA AWR System Time Percentages DBA AWR System Time Summary DBA AWR Tablespace Usage DBA AWR Wait Class by Time DBA AWR Wait Event Summary DBA AWR Wait Event Summary (active session history) DBA Alert Log DBA Archive / Redo Log Rate DBA Automated Maintenance Tasks DBA Blocking Sessions DBA CPU Benchmark1 DBA CPU Benchmark2 DBA CPU Benchmark3 DBA Dependencies (used by) DBA Dependencies (uses) DBA Editioned Object Summary DBA Editions DBA External Table Creation DBA Feature Usage Statistics DBA Hierarchical Profiler Data DBA Index Columns DBA Jobs DBA Log Switches DBA Objects DBA Parameters DBA Profiler Data DBA Redo Log Files DBA Registry SQL Patch DBA Result Cache Objects and Dependencies DBA Result Cache Statistics DBA SGA Active Session History DBA SGA Blocking Session Summary DBA SGA Buffer Cache Object Usage DBA SGA CPU Load (active session history) DBA SGA Memory Allocation DBA SGA SQL Execution Plan History DBA SGA SQL Performance Summary DBA SGA Target Advice DBA SGA Wait Event Summary (active session history) DBA SGA+PGA Memory Configuration DBA Scheduler Jobs DBA Segments DBA Session Longops DBA Table Columns DBA Table Modifications DBA Tablespace Usage DBA Text Search DBA Trace File Contents