OCCI Oracle C Call Interface

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OCCIOracle C Call Interface

• Krzysztof Nienartowicz
• DB Workshop
• January 29-31, 2002

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Overview

• Architectural overview
• Occi typical usage, development cycle
• Issues to solve, problems
• Tools, techniques used to understand OCCI
  internals

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General Architecture overview

• Associative ODMG like access using Refltgt
• OCCI is a wrapper on top of OCI and Oracle
  internal calls
• Set of C base classes, utility classes
• templates
• binary libraries

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Architectural overview. cont.

• OCCI is composed of 25 classes 30 classes of
  Oracle Data Cartridge Interface (ODCI)
  definitions for schema handling
• Refltgt access and root PObject classes act as a
  interface with hidden implementation delegated to
  RefImpl and PObject binary packaged
• plus utility classes to handle oracle native
  types
• Connections, db environment

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Architectural overview. cont.

• innerNode as a user type. N1,..,N10 are private
  innerNode_C members
• Access via get, set or as a public ones, OTT
  dependent

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Architecture overview, cont. 2

• STL dependencies
• Binary and string types represented as STL
  stdvectors and stdstrings
• May hit the performance if a conversion (due to
  type casting) is done under the hood
• No difference between const and non-const access
  patterns

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Typical, application flow
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OCCI Development cycle

• DDL driven, one must have DB schema defined first
• Two main cycles with given approach
• Schema definition, schema tuning phase
• Standard 3gl object oriented methodologies for
  the latter phase

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OCCI Development cycle, 2

• Schema definition - DDL/SQL

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OCCI Development cycle, 3
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OCCI Development cycle, 4
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Occi current problems, issues, tweaks

• Oracle production/bug fix cycle dependency
• Ball on the Oracle side
• Small leaks escalation, cache settings dependent
• Refltgt const, internal memory initialisation
  problems
• Prefetching problems
• Users responsibility to delete embedded objects
• Unnamed exceptions thrown sometimes, segmentation
  faults instead of exceptions occur

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Bloating memory (cache?) problem

• Memory consumption of a trivial, very small
  object linked list iteration
• Appears for many accesses for certain cache
  settings
• Memory growth is access related not accessed
  objects size related
• Benchmarking consequences

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Occi memory problems detection

• Unistd.h sbrk(0) very helpful
• mpatrol package
• Mpatrol, mptrace, mprof
• Dynamic hooks to the OS (libc, stdc) memory
  calls with no code changes, recompilation on UX
• Sophisticated memory monitoring, profiling with
  logging and post mortem analysis

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Mpatrol usage

• Memory graphical profiling with mprof
• Visual tracing with mptrace
• Textual form, calls graph
• Memory leaks, resizing, deleting, allocating
  stats

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mpatrol

• Easier tracing down of inefficiencies, in example
  beneath, extracted dereferencing of the app
  object.

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Other mpatrol benefits
MEMSET memset (0x002240C8, 68 bytes, 0x00)
--- 0xFEE72F34 kghualloc600 0xFED0B20C
kohalmc480 0xFED0B020 kohalc1836 0xFEA0D63C
kadlal80 0xFEDACFC8 kopldsgen40 0xFEA15DB0
kadgscval228 0xFEA15614 kadattrget4396 0xFE9A3
9C0 OCIAnyDataAttrGet68 0x000A14A0
oracleocciNumber occiAnyDataImplgetNumber(
)const104 0x00064E58 void innerNode_CreadSQL(o
racleocciAnyData)32 0x00064D20
voidinnerNode_CreadSQL(void)192 0xFECF3750
kodpunp3700 0xFED02794 kocdsun460 0xFECF6F7C
kocgpn22720 0xFECF64D4 kocgpn80 0xFED32B48
OCIObjectPin3872 0x00088F94 oracleocciPObjec
toracleocciRefImplpin()168 0x0005F204
innerNodeoracleocciRefltinnerNodegtoperator-gt
()44 0x0005C37C long BenchAppltlonggtCheckInnerC
ycle()212 0x000578D0 void BenchAppltlonggtDoRea
d()720 0x0005738C int BenchAppltlonggtRun()52
0x0005F78C main92

• Occi internals quasidebugging, i.e. allows to
  understand occi-oci-oracle layering better

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Summary

• The Refltgt associative access the main OCCI
  advantage in comparison to other methods
• Waiting for the next release to proceed with
  benchmarks
• Cache handling improvement
• Bugs to be removed
• Inconsistencies to be removed (i.e. ott naming)
• For mpatrol check http//www.cbmamiga.demon.co.uk
  /mpatrol