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debug-slow-sql

Data & analytics

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Updated 10-15 09:33

About this skill

Debug Slow SQL / OData

Find the root cause of a slow ABAP SQL or Fiori-Elements OData request and propose a fix — driving ARC-1's diagnostics first (GUI-free), then escalating to SAP GUI / Fiori apps only when the deeper signal needs them. The goal is not "it's slow" but why: which statement, what it scans, and what to change.

Use this when the user reports a slow report/transaction, a slow OData/Fiori list, a long-running CDS view, a timeout/dump under load, or "this query got slow after …".

Inputs (ask only for what's missing)

  • What is slow — one of: an OData URL (copy from the browser Network tab), a CDS view / DDLS name, an ABAP program / class / report, a transaction code, or a table + access pattern.
  • How slow / how often — a single slow call vs. slow-under-load vs. intermittent. (Routes you to per-request vs. aggregate analysis.)
  • Reproducible? — can the user re-trigger it on demand (needed to arm a live trace)? On which system (DEV/QA/PROD) and as which SAP user?
  • Recent change? — new code, new data volume, a transport, an index drop. Narrows the search fast.

If you only have a vague "X is slow", get the OData URL or the object name first — everything below keys off it.

The diagnostic ladder — stop at the rung that explains it

Work top-down. Each rung is cheaper than the next and usually tells you whether to descend.

Reachability — don't promise a plan you can't reach. Rungs 3–4 (profiler, ST05) need SAP_ALLOW_WRITES to arm, S_ADT_RES with URI coverage for the trace resources, and the trace tools' backend authorizations (confirm with STAUTHTRACE) — and don't exist on NW 7.50. If arming returns writes disabled or a 403, say so and stop at rung 2: odata_perf + cds_sql + SAPQuery already pin a DB-bound root cause GUI-free. Tier-3–4 (the exact statement + execution plan) then depends on Basis/config, so hand the user the precise ST05/SAT steps below instead of pretending you reached the plan.

0. Orient (no execution)

  • SAPContext(action="deps", type="<type>", name=…) / SAPRead(type="DDLS", name=…) — read the CDS/ABAP source. Eyeball it for the usual suspects before measuring: LIKE '%term%' (leading wildcard = no index), SELECT … FROM with no WHERE on a key, SELECT *, nested SELECT in a LOOP (N+1), client-side filtering, missing FOR ALL ENTRIES pre-check, calculated fields forcing a full scan.
  • SAPContext(action="impact", type="DDLS", name=…) — the CDS stack (projection → base views → tables). The slow view is often a thin projection over a heavy base.
  • Find the generator, not just the literal SQL. A slow LIKE '%…%'/scan is often generated — by a search help, SADL/RAP, or a framework — not hand-written, so a grep/where-used for the literal SELECT comes up empty. Trace the generator instead: for a value-help / type-ahead screen, the search help (DD30L.SELMETHOD + FUZZY_SEARCH, DD32S fields) and its DSH/SADL classes (CL_DSH_*, the F4→WHERE conversion) via SAPSearch/SAPNavigate/SAPRead. For an OData service, find its implementation: a V4/RAP binding → SAPRead(type="SRVB", name=…) → the service definition → the CDS view (then use cds_sql, rung 2). The binding (SRVB) name often differs from the URL's service path — if SRVB 404s, SAPSearch the service name to find the actual binding, or read the service definition (SRVD) directly for its expose … as entities. A classic SEGW / Gateway V2 service has no CDS → find the DPC class (SAPSearch "<SERVICE>_DPC*", read its *_get_entityset / *_get_entity / expand / resolve_navigation_path methods) and skip rung 2. (Don't confuse SE91/WBMESSAGES, which loads one message class in memory and searches with CS, with a search-help path that issues a real DB LIKE.)

1. Where did the time go? (one cheap call)

For an OData / Fiori request:

SAPDiagnose(action="odata_perf", url="/sap/opu/odata4/sap/…/Entity?$filter=…")

Read the verdict:

  • db (gwappdb dominates) → the CDS/SQL query is the cost → go to rung 2.
  • app (gwapp ≫ gwappdb, or gwappdb absent) → ABAP/SADL logic, not the DB. Do not ST05-hunt for a slow query — find what implements the service (rung 0) and trace it (rung 3). Classic culprit is an $expand N+1 — isolate it by re-probing the URL with vs without $expand/$select and watch gwapp move.
  • framework (gwfw; on 7.50 often only gwhub) → metadata / first-call / cold cache → re-probe warm. If only gwhub is present, you do not have a DB/app split yet; descend to a trace if it is not just cold cache.
  • auth (icfauth) → ICF/DCL authorization overhead.
  • unknown → no usable Gateway timing at all; confirm the URL is an OData/Gateway service on the SAP host.

(odata_perf needs SAP_ALLOW_DATA_PREVIEW; url must be a host-relative OData path under /sap/opu/odata or /sap/opu/odata4 on the SAP host ARC-1 connects to — other paths are rejected. It does a GET, so use the entity/list request from the Network tab, not a $batch POST.)

2. DB-bound → see and measure the actual SQL

  • SAPDiagnose(action="cds_sql", name="I_TheView") — the native CREATE VIEW the CDS compiles to (read-only; verified on 7.50/758/816). Now you see the real joins, CASTs, COALESCEs, and whether a sub-view drags in extra tables.
  • SAPQuery(sql="SELECT … FROM <cds-or-base> WHERE <the filter>") — returns columns/rows plus datapreview metrics: queryExecutionTimeMs, totalRows (total matches), rowsReturned, and the executedQueryString. Run it with the real filter values from the slow request: a large totalRows / queryExecutionTimeMs for a small useful result = a scan/selectivity problem. It does not expose the HANA execution plan or buffer state — use ST05/HANA for those. A SAPQuery that times out is itself evidence of an unbounded scan — record the timeout as the signal, don't just retry with a smaller maxRows. (Needs SAP_ALLOW_FREE_SQL for freestyle SQL; multi-column WHERE via SAPRead(type="TABLE_QUERY") needs SAP_ALLOW_DATA_PREVIEW.)
  • Equality also slow? It's the view, not your filter. If SAPQuery with an exact WHERE key = '…' is as slow as a LIKE '%…%' (both tens of seconds), the LIKE is a red herring — the cost is the CDS itself: a wide SELECT DISTINCT, a deep join the filter can't start from (the filtered field isn't index-leading), or an aggregate / $count=true. cds_sql shows the join order; the fix is to invert the join so the selective table leads, trim the DISTINCT/aggregate out of the list projection, or drop $count=true on a large scan — not to touch the LIKE.
  • Compare signals: probe the OData URL, then run SAPQuery on the underlying CDS/base — if queryExecutionTimeMs is close to the OData gwappdb, the DB query is the cost; if OData is slow but the query is fast, it's the SADL/framework layer above. For the exact statement + execution plan, descend to ST05.
  • Recommending a HANA full-text / CONTAINS / fuzzy fix? You can't A/B-test it with SAPQuery — the ADT freestyle endpoint is Open-SQL-only and rejects CONTAINS(...) / … CP '*x*' (400 "(" is not allowed). Prove it instead with an ST05 trace during a live reproduce of the real feature, or a one-off ABAP probe report. First confirm the table even has a full-text index: SAPQuery(sql="SELECT indexname, full_text FROM dd12l WHERE sqltab = '<TABLE>'") → full_text = 'X'.

3. App-bound → ABAP profiler trace (which code, which tables)

SAPDiagnose(action="traces")                                  # list recent profiler traces
SAPDiagnose(action="traces", id="<id>", analysis="hitlist")    # hottest call paths
SAPDiagnose(action="traces", id="<id>", analysis="dbAccesses") # which tables, counts, buffered?

The dbAccesses view tells you which tables a request hit and how often (N+1 shows up as a huge count on one table). The hitlist tells you the ABAP hot path. ARC-1 can arm a profiler trace request itself — SAPDiagnose(action="trace_start", …), then trace_requests to list and trace_cancel to clean up — or record one in SAT/ST12; then list/analyze it with the traces action above.

Two caveats trace_start itself flags — heed them: (1) an HTTP trace captures the user's very next matching HTTP call, so after arming make no other ARC-1/MCP calls until the user has reproduced — your own ADT calls will consume the trap. (2) For HTTP/OData traces on HANA the profiler is weak: hitlist/statements are usually empty (or 400 "Data is invalid…"), and business tables hide inside a <DB Access from Kernel> bucket — use dbAccesses only for "did we touch table X, how often", and use ST05 (rung 4) for the actual OData SQL + timings. The profiler is richest for dialog/report/RFC traces of ABAP-side code.

4. The exact SQL + plan → ST05 SQL trace

ARC-1 can arm/disarm the ST05 SQL trace and point you to the records (it can't read the records over ADT — SAP has no SQL-record API; record viewing is the TMC Fiori app / SAP GUI ST05):

SAPDiagnose(action="sql_trace_state")                                   # is a trace already on?
SAPDiagnose(action="set_sql_trace_state", sqlOn=true, user="<SAPUSER>") # arm, filtered to the user (needs SAP_ALLOW_WRITES)
#   → user reproduces the slow request now ←
SAPDiagnose(action="sql_trace_directory")                               # SAP's "SQL Trace Analysis" deep-link
SAPDiagnose(action="set_sql_trace_state", sqlOn=false)                  # always disarm when done

Then read the records (see "SAP GUI / Fiori escalation"). The record list gives you the exact SELECT, its duration, rows fetched, the object, and (in ST05) the EXPLAIN / execution plan + buffer state. Available on 758/816; not on NW 7.50 (the /st05/trace ADT API returns 404 there — use SAP GUI ST05).

Reading the records (there is no sql_trace_records/sql_trace_read ADT action — sql_trace_directory only returns the viewer link): open the deep-link (TMC "SQL Trace Analysis") or SAP GUI ST05 → Display Trace → pick the app server + your trace file → sort by Duration desc → per row read the SQL text, Duration, Records (rows fetched), Object (table/view); double-click the slowest → Explain for the HANA plan. Look for: extra hits on association/text tables (SADL expansion), repeated identical SELECTs (N+1), or Records ≫ visible rows (selectivity).

If a perf endpoint 403s with "Service cannot be reached", ARC-1 surfaces an icf-service-inactive hint — activate the named SICF node (/sap/bc/stmc for the trace UI) in tcode SICF.

5. Static check (anytime)

SAPDiagnose(action="atc", type="<type>", name=…, variant="PERFORMANCE_DB") — flags perf anti-patterns statically (it won't catch a runtime LIKE scan that depends on data, but it's free and catches the obvious ones).

SAP GUI / Fiori escalation (when ARC-1's GUI-free signals aren't enough)

ARC-1 is GUI-free up to the point of reading SQL-trace records and execution plans — for those, escalate. Tell the user exactly what to open and what to look for; or, if you have a desktop/Chrome MCP and authorization, drive it yourself (never on PROD without explicit sign-off).

Tool Where What it gives you that ARC-1 can't
ST05 (SQL/RFC/buffer/enqueue trace) SAP GUI The recorded SELECTs with duration + rows; "Explain" → the DB execution plan; identical-/similar-statement grouping; buffer hits. The ground truth for "which statement and why".
SQL Trace Analysis Fiori app (the sql_trace_directory deep-link) The same ST05 records in a browser (TMC) — use when SAP GUI isn't available. Needs /sap/bc/stmc SICF active.
ST12 / SAT SAP GUI Combined ABAP+SQL trace with aggregation — best for "where does the time really go" across app+DB in one capture.
DBACOCKPIT / HANA SAP GUI / HANA Studio / DBeaver EXPLAIN PLAN, PlanViz, M_SQL_PLAN_CACHE, table/index sizes, missing-index hints, optimizer stats freshness. The HANA-side root cause (column-store scan, no pruning, stale stats).
ST22 / SM50 / SM66 SAP GUI Dumps (e.g. TIME_OUT, TSV_* memory) and what work processes are stuck on under load.
SE11 / SE14 SAP GUI Indexes on the table, their fields, and whether the slow WHERE matches a usable index prefix.
ABAP Cross Trace ADT (/sap/bc/adt/crosstrace/*, 758+) RAP/OData-aware cross-layer trace incl. OData V4 request types — the strategic ADT-native record reader (ARC-1 follow-up; not yet a tool).

Capturing an OData request for odata_perf: browser DevTools → Network → click the slow $batch/entity request → copy the path after the host (e.g. /sap/opu/odata4/sap/zsrv/…/Entity?$filter=…&$top=…). That path is the url argument.

Root-cause catalog (pattern → confirm → fix)

Symptom in the trace/SQL Likely cause Confirm Typical fix
Huge rows fetched ≫ rows shown; long duration Full scan / poor selectivity cds_sql shows no indexed WHERE; SAPQuery totalRows large / ST05 high rows fetched Add a WHERE on indexed fields; add a secondary index (SE11); push the filter into the CDS
LIKE '%term%' Leading-wildcard = index unusable Read DDLS/ABAP source Search help / fuzzy (HANA) / full-text index; anchor the pattern; pre-filter
Same table hit thousands of times N+1 (SELECT in LOOP) traces dbAccesses shows a giant count on one table FOR ALL ENTRIES / a join / read-all-then-loop; RAP: prefetch
SELECT * then use 2 fields Over-fetch cds_sql / source Select only needed fields; trim the CDS projection
Fast in DEV, slow in PROD Data volume / stale stats / different plan Compare EXPLAIN + table sizes (DBACOCKPIT) Refresh optimizer stats; add index; partition
gwappdb small but OData slow SADL / determinations / virtual elements / auth (DCL) odata_perf verdict app/auth; profiler hitlist Move logic to the DB/CDS; simplify DCL; cache; avoid per-row ABAP virtual elements
Slow only first call Metadata / cold cache odata_perf verdict framework; re-probe warm Expected; warm-up; don't optimize the query
TIME_OUT / memory dump under load Unbounded result / missing paging ST22 + ST05 Server-side paging ($top/$skip); add filters; package the work

Worked example (real, a4h S/4HANA 2023)

A "message-text search screen is slow" complaint. The query behind it:

SAPQuery(sql="SELECT sprsl, arbgb, msgnr, text FROM t100 WHERE text LIKE '%error%'")
→ { totalRows: 12549, queryExecutionTimeMs: 49.086, rowsReturned: 100,
    executedQueryString: "SELECT … FROM T100 WHERE TEXT LIKE '%error%' … UP TO 100 ROWS" }

Read it: 12 549 rows matched a leading-wildcard LIKE '%…%' on a non-indexed text column → a full table scan (the index is unusable because the pattern starts with %). The result the user actually wanted was a handful of rows. Fix: drop the leading wildcard (anchor the search) / add a search help or full-text index / pre-filter on an indexed field first. For the HANA plan + rows-fetched, arm an ST05 trace (rung 4), reproduce, and open the directory deep-link.

This is the simple case — a single-table scan where the leading wildcard really is the bottleneck. On a wide CDS view it often is not: if an exact-match WHERE key = '…' is just as slow as the LIKE, the cost is the view's joins / DISTINCT / $count, not the wildcard (rung 2, "Equality also slow?"). Measure both before you blame the LIKE.

Output

Deliver a tight diagnosis, not a tool log:

  1. Verdict — DB / app / framework / auth, with the number that proves it (e.g. "gwappdb 412 ms of gwtotal 480 ms"). Cite the SAP figure (gwtotal/gwappdb), never wallClockMs: wall-clock also counts network/MCP/proxy (odata_perf returns that gap as clientWaitMs), so when clientWaitMs dwarfs gwtotal the latency is the landscape, not the query.
  2. The statement — the offending SQL (from cds_sql / ST05) and what it scans (SAPQuery totalRows / ST05 rows fetched, the table, the missing index).
  3. Root cause — one sentence, mapped to the catalog above.
  4. Fix — concrete and minimal (the index to add, the filter to push down, the N+1 to collapse), with the cheapest option first and the trade-off named.
  5. Evidence — the exact ARC-1 calls run + any ST05/HANA-plan capture, so the user can re-verify.

Always disarm any trace you armed. On PROD, prefer read-only signals (odata_perf, cds_sql, SAPQuery, read-only traces) and get explicit sign-off before arming an ST05 trace or touching state.