Mainframe Performance & Scalability SME

Arm; City Of London; Hybrid; GBP 111,000 - 166,000; Full time

Job summary

Arm is seeking a senior Mainframe Performance & Scalability SME to support a focused assessment for a major UK financial services client. The role focuses on Db2, CICS, and mainframe capacity, with an emphasis on diagnosing scalability risk from production evidence and leading client conversations with architects and operations SMEs.

The assignment covers Db2 estate analysis, potential refactoring, observability improvements, and capacity planning across IBM Z platforms.

Qualifications

• Experience with Db2 for z/OS performance and scalability in an enterprise environment.
• Ability to diagnose scalability risk from production evidence and lead technical discussions with client architects.
• Strong understanding of CICS, Db2, and mainframe capacity management in large-scale systems.
• Experience with observability tooling and interpreting CPU/MSU/I/O metrics to drive remediation.

Responsibilities

• Lead technical conversations with client architects and operations SMEs to assess scalability risk.
• Analyze Db2, CICS and workload performance to identify remediation paths.
• Evaluate TLS/cryptography impact and infrastructure changes for performance.
• Produce actionable recommendations and clear evidence-based justification for improvements.

Skills

Db2 for z/OS performance

CICS performance

Mainframe capacity planning

RMF/SMF analysis

TLS / IBM Z cryptography

Observability & diagnostics

Tools

OMEGAMON

MainView

BMC AMI

RMF

SMF

Datadog

Job description

Mainframe Performance & Scalability SME

6-Month contract - Inside IR35 - market rate

London based - hybrid working - 2-3 days a week onsite

Finance sector

We are looking for a senior Mainframe Performance & Scalability SME to support a short, focused assessment for a major UK financial services client.

This is not a general mainframe systems-programming role. We need someone who can take incomplete production evidence, diagnose where scalability risk genuinely sits, and confidently lead technical conversations with experienced client architects, platform engineers and operations SMEs.

The assignment

The client operates a long-established pension administration platform on IBM mainframe technology. The assessment is looking at how the platform will behave under future business growth and concentrated demand events, and what should be:

• tuned or optimised;
• archived or cleaned up;
• moved away from the transactional core;
• re-engineered;
• monitored differently; or
• addressed through additional capacity.

The work includes a particular focus on Db2, CICS, mainframe capacity, batch processing, workload attribution and observability.

There is also a historic question around a data‑centre / IBM Z16 migration, increased TLS processing and an associated increase in general‑purpose MSU consumption, which needs to be assessed from evidence rather than assumed causation.

Skills & Experience:

• Db2 for z/OS performance and scalability
  • table and index growth;
  • index design and access-path performance;
  • RUNSTATS, REORG and statistics strategy;
  • access-path regression;
  • buffer-pool performance;
  • GETPAGEs and I/O;
  • locking, timeouts and deadlocks;
  • high-cost SQL and packages;
  • data archival / lifecycle strategies;
  • performance behaviour as database volumes grow.
  • We particularly want someone able to look at an established Db2 estate and determine whether there is accumulated performance or data-management debt that should be remediated before simply adding infrastructure.
• CICS performance
  • Strong understanding of:
  • CICS-to-Db2 workload behaviour;
  • transaction / program / package correlation;
  • threadsafe execution and open TCBs;
  • Db2 thread reuse / DB2ENTRY configuration;
  • commit and syncpoint behaviour;
  • transaction chattiness and excessive data retrieval;
  • identifying where legacy access patterns should be re‑engineered rather than simply tuned.
• Mainframe capacity and workload management
  • Experience with:
  • RMF and SMF analysis;
  • WLM service policies and service classes;
  • MSU utilisation and workload attribution;
  • capping and group-capacity behaviour;
  • SCRT / sub-capacity licensing considerations;
  • separating CPU consumption from elapsed‑time constraints;
  • critical and non‑critical batch;
  • identifying concurrent workload peaks and genuine capacity headroom.
• TLS / cryptography / IBM Z
  • Useful experience investigating performance changes associated with:
  • IBM Z hardware migrations;
  • System SSL / AT‑TLS;
  • CPACF;
  • Crypto Express / ICSF;
  • TLS handshake versus encryption workload;
  • zIIP versus general‑purpose processing eligibility;
  • validating pre/post‑migration CPU or MSU changes.
  • The consultant should be comfortable challenging assumptions such as "TLS caused an additional 50 MSU" and establishing what evidence is needed to prove the actual cause and recoverable benefit.
• Observability and diagnostics
  • We need somebody who can connect:
  • business event → application / CICS transaction → job or package → Db2 object → CPU / MSU / I/O / locking → elapsed time
• Tools such as the following would be valuable:
  • OMEGAMON
  • MainView / BMC AMI
  • RMF / SMF
  • Db2 performance tooling
  • CICS monitoring
  • Dynatrace
  • Datadog
  • other mainframe APM / telemetry platforms.