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mainframe-os
mainframe OS with sysplex clustering
IBM z/OS
System
Techniques · 10
Primitives · 34
mainframe-os
Batch checkpoint restart
distributed · medium: Large batch jobs (end-of-day, settlement, payroll runs) that checkpoint and restart idempotently
Clock synchronization
distributed · medium: Estimate a clock's offset from four timestamps, filter out queueing noise, and steer the clock smoothly; NTP gets about a millisecond, PTP with hardware timestamps under a microsecond.
›
Durable job queue
distributed · medium: Persisted tasks that workers lease for a visibility timeout, ack on success and retry with backoff; at-least-once execution that survives worker and queue crashes.
›
Primary-backup replication
distributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.
›
Shared data cluster lock cache
distributed · medium: Shared lock and cache structures in a coupling facility: global lock negotiation and cross-invalidation of locally cached pages across cluster members
Two-phase commit
distributed · medium: Atomic commit across shards: participants durably vote yes, then the coordinator logs and broadcasts one decision; blocks if the coordinator is lost.
›
ARIES recovery
storage · medium: Three-pass crash recovery (analysis, redo, undo) for steal/no-force buffer pools; repeats history, then rolls back losers with compensation log records.
›
Write-ahead log
storage · low: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.
›
Resource usage accounting
hardware-os · low: Cgroup/procfs/GPU counters sampled into per-workload usage
Fencing tokens
distributed · low: A number that grows with every lock grant and is checked by the protected resource, so a paused ex-holder's late write is rejected.
›
Context switching
hardware-os · low: Handing a core to another task by saving and loading registers, stack and address space; the hidden cache and TLB cost outweighs the direct one.
›
Hardware virtualization kvm
hardware-os · low: VT-x/AMD-V via KVM: vCPU run loop, VM exits, MMIO emulation
Interrupt handling
hardware-os · low: How a device signal reaches a CPU handler through an interrupt controller and vector table, and how top/bottom halves, polling switch-over and coalescing keep load bounded.
›
Io request scheduling
hardware-os · low: Reorder and batch I/O by device position (elevator/SCAN, deadline) for seek-bound media
System call interface
hardware-os · low: The controlled gate between user code and the kernel: number and arguments in registers, a trap instruction, a validated handler, a result or error code.
›
Virtual memory and the TLB
hardware-os · low: How page tables and TLBs translate every address, what TLB reach means, and when 2 MiB or 1 GiB huge pages pay off on Linux.
›
Authorization models (RBAC, ABAC, R…
security · low: How to decide who may do what to which object; roles for coarse rules, relationships for sharing, and checks on every object.
›
B+ tree
storage · low: Balanced high-fanout search tree with all values in linked leaves; the default on-disk index for point lookups and range scans.
›
Deadlock detection
storage · low: Find transactions waiting on each other in a cycle (wait-for graph), abort one, or order lock requests so no cycle can form.
›
Index-free adjacency
storage · low: Store each node's edges as direct references to neighbouring records, so a hop costs O(degree) pointer reads instead of an index search; know when plain tables or CSR beat it.
›
Two-phase locking
storage · low: Transactions take shared/exclusive locks and release none until they stop acquiring; strict 2PL holds them to commit and guarantees serializability.
›
Idempotency keys
finance · low: Client-chosen unique key per logical operation, stored with a request fingerprint and the final response, so retries replay the first result instead of acting twice.
›
Cron scheduling
systems · low: Cron expression parsing and next-fire-time computation, with catch-up and time-zone rules
+ 3 more techniques
+ 18 more primitives
System
Techniques · 10
Primitives · 34
mainframe-os
Batch checkpoint restart
distributed · medium: Large batch jobs (end-of-day, settlement, payroll runs) that checkpoint and restart idempotently
Clock synchronization
distributed · medium: Estimate a clock's offset from four timestamps, filter out queueing noise, and steer the clock smoothly; NTP gets about a millisecond, PTP with hardware timestamps under a microsecond.
›
Durable job queue
distributed · medium: Persisted tasks that workers lease for a visibility timeout, ack on success and retry with backoff; at-least-once execution that survives worker and queue crashes.
›
Primary-backup replication
distributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.
›
Shared data cluster lock cache
distributed · medium: Shared lock and cache structures in a coupling facility: global lock negotiation and cross-invalidation of locally cached pages across cluster members
Two-phase commit
distributed · medium: Atomic commit across shards: participants durably vote yes, then the coordinator logs and broadcasts one decision; blocks if the coordinator is lost.
›
ARIES recovery
storage · medium: Three-pass crash recovery (analysis, redo, undo) for steal/no-force buffer pools; repeats history, then rolls back losers with compensation log records.
›
Buffer pool
storage · medium: The database's own page cache (frames, page table, pin counts, dirty bits, replacement) so it, not the OS, controls eviction, write order and I/O.
›
Cache invalidation
systems · medium: Make writes remove cached copies by key, group tag or prefix, broadcast the removal to every node, and guard refills with tokens so stale values never return.
›
Fair share scheduling
systems · medium: Dominant resource fairness and hierarchical fair-share queues
Write-ahead log
storage · low: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.
›
Resource usage accounting
hardware-os · low: Cgroup/procfs/GPU counters sampled into per-workload usage
Fencing tokens
distributed · low: A number that grows with every lock grant and is checked by the protected resource, so a paused ex-holder's late write is rejected.
›
Context switching
hardware-os · low: Handing a core to another task by saving and loading registers, stack and address space; the hidden cache and TLB cost outweighs the direct one.
›
Hardware virtualization kvm
hardware-os · low: VT-x/AMD-V via KVM: vCPU run loop, VM exits, MMIO emulation
Interrupt handling
hardware-os · low: How a device signal reaches a CPU handler through an interrupt controller and vector table, and how top/bottom halves, polling switch-over and coalescing keep load bounded.
›
Io request scheduling
hardware-os · low: Reorder and batch I/O by device position (elevator/SCAN, deadline) for seek-bound media
System call interface
hardware-os · low: The controlled gate between user code and the kernel: number and arguments in registers, a trap instruction, a validated handler, a result or error code.
›
Virtual memory and the TLB
hardware-os · low: How page tables and TLBs translate every address, what TLB reach means, and when 2 MiB or 1 GiB huge pages pay off on Linux.
›
Authorization models (RBAC, ABAC, R…
security · low: How to decide who may do what to which object; roles for coarse rules, relationships for sharing, and checks on every object.
›
B+ tree
storage · low: Balanced high-fanout search tree with all values in linked leaves; the default on-disk index for point lookups and range scans.
›
Deadlock detection
storage · low: Find transactions waiting on each other in a cycle (wait-for graph), abort one, or order lock requests so no cycle can form.
›
Index-free adjacency
storage · low: Store each node's edges as direct references to neighbouring records, so a hop costs O(degree) pointer reads instead of an index search; know when plain tables or CSR beat it.
›
Two-phase locking
storage · low: Transactions take shared/exclusive locks and release none until they stop acquiring; strict 2PL holds them to commit and guarantees serializability.
›
Idempotency keys
finance · low: Client-chosen unique key per logical operation, stored with a request fingerprint and the final response, so retries replay the first result instead of acting twice.
›
Cron scheduling
systems · low: Cron expression parsing and next-fire-time computation, with catch-up and time-zone rules
PID controller
robotics · low: Drive a measured value to a setpoint with three terms on the error: proportional, integral, derivative. The default feedback loop for motors, heaters, drones and gimbals.
›
Phase-locked loop (digital)
signal-processing · low: Feedback loop that locks a local oscillator to the phase and frequency of an input tone; the core of carrier recovery, clock recovery and GNSS tracking.
›
Robust statistics
statistics · low: Location and scale estimates (median, MAD, trimmed mean, Huber M-estimator) that stay correct when a minority of the data is garbage.
›
Dead-letter queue
distributed · low: A side queue for messages that keep failing: after N delivery attempts or a permanent error, park them with the reason so the main queue keeps moving.
›
Leases
distributed · low: A lock that expires on its own: bounded-time ownership that survives crashes and partitions, given bounded clock drift and fencing tokens on writes.
›
Exponential backoff with jitter
systems · low: Retry after delays that grow geometrically and are randomized, so failed clients spread out instead of hammering a recovering service in synchronized waves.
›
Health checking
systems · low: Decide per backend whether to route to it using probes and real-traffic errors, with consecutive-count hysteresis, capped ejection and a panic fallback.
›
fsync, O_DSYNC and O_DIRECT
hardware-os · low: What fsync, fdatasync, O_DSYNC, O_DIRECT and F_FULLFSYNC really guarantee on Linux and macOS, and the exact call sequences for crash-safe files.
›
LRU and CLOCK
systems · low: LRU evicts the least recently used entry via hash map plus linked list; CLOCK approximates it with a reference bit, so hits take no lock.
›
S3-FIFO
systems · low: Three FIFO queues (small, main, ghost) that evict one-hit wonders quickly and keep reused objects; low miss ratios with no list moves on hits.
›
Message sequence numbers
distributed · low: A per-stream counter on every message lets the receiver detect loss, duplicates and reordering, ack cheaply and resume after reconnect with "send from N".
›
Publish subscribe event bus
systems · low: In-process or on-box topic bus decoupling producers and consumers with bounded queues
d-ary heap
data-structures · low: Array heap with d children per node (d = 4 typical): half the binary heap's depth, siblings in one cache line, faster priority queues.
›
Exponential smoothing (ETS, Holt-Wi…
statistics · low: Forecast by keeping a few running states (level, trend, seasonal) updated by a fraction of each forecast error; O(1) memory per series and a strong baseline.
›
CRC32C checksums
hardware-os · low: The Castagnoli CRC-32 with dedicated instructions on x86 (SSE4.2) and ARMv8. It is the standard fast integrity check for storage blocks, logs and network frames.
›
SIMD programming
hardware-os · low: Process 4-16 lanes per instruction with AVX2, AVX-512 or NEON via Rust std::arch, with runtime dispatch and a portable fallback.
›
PRNGs (PCG, xoshiro)
numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.
›
Cryptographic hashes (SHA-2, BLAKE3)
security · low: Collision-resistant fingerprints of data; SHA-256 for interoperability, BLAKE3 for speed, HMAC/HKDF for keyed uses.
›
Copy for AI
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