Dealing with resource contention

The major resources used or managed by CICS® consist of the following:

Contention at lower levels prevents full use of higher-level resources. To avoid or reduce resource contention, you can:

Two sets of symptoms and solutions are provided in this section. The first set provides suggested solutions for poor response (see Solutions for poor response time), and the second set provides suggested solutions for a variety of resource contention problems (see Symptoms and solutions for particular resource contention problems).

Solutions for poor response time

Table 10 shows four levels of response time, in decreasing order of severity. The major causes are shown for each level together with a range of suggested solutions. Your first step is to check the causes by following the advice given in Assessing the performance of your system. When you have identified the precise causes, the relevant checklist in Performance checklists tells you what solutions are available and where to find information in Part 4 of this book on how to implement the solutions.

Table 10. CICS response time checklist
Major Causes Overall Solution
Level 1: Poor response at all loads for all transactions
High level of paging Reduce working set, or allocate more real storage
Very high usage of major resources Reconsider system resource requirements and redesign system

Check for application errors and resource contention

Level 2: Poor response at medium and high loads
High level of paging Reduce working set, or allocate more real storage
High processor usage Reduce pathlength, or increase processor power
High DB or data set usage Reorganize data sets, or reduce data transfer, or increase capacity
High communication network usage Reduce data transfer, or increase capacity
TP or I/O access-method constraint Increase buffer availability
CICS limit values exceeded Change operands, or provide more resources, or check if errors in application
Level 3: Poor response for certain transactions only
Identify common characteristics As for level 2
Lines or terminal usage Increase capacity, or reduce data transfer, or change transaction logic
Data set usage Change data set placement buffer allocations or change enqueue logic or data set design
High storage usage Redesign or tune applications
Same subprograms used by transactions Redesign or tune application subprograms
Same access method or CICS features used by transactions Reallocate resource or change application. Reevaluate use of feature in question
Limit conditions Reallocate resource or change application
Level 4: Poor response for certain terminals
Check network loading as appropriate Increase capacity of that part of network
Check operator techniques Revise terminal procedures
Check CEDA terminal definitions Redefine CEDA terminal definitions

Symptoms and solutions for particular resource contention problems

This section presents a general range of solutions for each type of constraint. You should:

  1. Confirm that your diagnosis of the type of constraint is correct, by means of detailed performance analysis. Methods of performance analysis describes various techniques.
  2. Read Tuning your CICS system for general advice on performance tuning.
  3. See the relevant sections in Part 4 of this book for detailed information on applying the various solutions.
  4. Improve virtual storage exploitation. This requires: Such a system can deliver better internal response times, while minimizing DASD I/O constraint and reducing processor utilization.

DASD constraint

Symptoms
Solutions

Communications network constraint

Symptoms
Solutions

Remote systems constraints

Symptoms
Solutions

Virtual storage constraint

Symptoms
Solutions

See the Virtual storage above and below 16MB line performance checklist for a detailed list of suggested solutions.

Real storage constraint

Symptoms
Solutions

See the Real storage performance checklist for a detailed list of suggested solutions.

Processor cycles constraint

Symptoms
Solutions

See the Processor cycles performance checklist for a detailed list of suggested solutions.

Related tasks
Identifying CICS constraints
Observing response times
Identifying storage stress
Identifying paging problems
Detecting storage violation
Dealing with limit conditions
Identifying performance constraints
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