1 © 2014 Julian Dyke juliandyke.com Advanced Diagnostics Revisited Julian Dyke Independent...

1 © 2014 Julian Dyke juliandyke.com

AdvancedDiagnosticsRevisited

Julian Dyke

Independent Consultant

UKOUG Conference 2014

© 2014 Julian Dyke juliandyke.com

WARNING

Much of the content of this presentation is undocumented and

unsupported by Oracle

Check with Oracle support before using any of these features in a

production environment

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Agenda

Trace Parameters Features and Hints Execution Plans Events ORADEBUG ALTER Statements

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© 2014 Julian Dyke juliandyke.com4

Trace


TraceV$DIAG_INFO Introduced in Oracle 11.1 Session-specific view reporting various diagnostic parameters

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VALUE

/u01/app/oracle/diag/rdbms/target/TARGET/trace/TARGET_ora_5556.trc

SELECT value FROM v$diag_infoWHERE name = 'Default Trace File';

Column Name Data Type

INST_ID NUMBER

NAME VARCHAR2(64)

VALUE VARCHAR2(512)

CON_ID NUMBER

Current trace file can be determined using:


TraceTRACEFILE_IDENTIFIER Parameter Introduced in Oracle 8.1.7 Appends specified suffix to trace file name Subsequent trace is immediately written to new file Can be updated unlimited number of times

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/u01/app/oracle/diag/rdbms/target/TARGET/trace/TARGET_ora_5556_TEST.trc

ALTER SESSION SET tracefile_identifier = 'TEST';

For example if the current trace file name is:

/u01/app/oracle/diag/rdbms/target/TARGET/trace/TARGET_ora_5556_TEST.trc

If the TRACEFILE_IDENTIFIER is set to "TEST":

Subsequent trace will be written to:

ORADEBUG SETTRACEFILEID TEST

TRACEFILE_IDENTIFIER can also be set using ORADEBUG:


TraceDBMS_SYSTEM.KSDWRT Procedure To write to trace files and/or alert log use:

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DBMS_SYSTEM.KSDWRT(

DEST NUMBER, -- 1 = Trace File, 2 = Alert LogTST VARCHAR2 -- Message

);

BEGINDBMS_SYSTEM.KSDWRT (1, ‘Output to trace file’);DBMS_SYSTEM.KSDWRT (2, ‘Output to alert log’);

END;

For example:


TraceDBMS_MONITOR - Overview Introduced in Oracle 10.1 Package to enable/disable trace and statistics Defined in $ORACLE_HOME/rdbms/admin/dbmsmntr.sql

Trace subroutines include: SESSION_TRACE_ENABLE / DISABLE DATABASE_TRACE_ENABLE / DISABLE CLIENT_ID_TRACE_ENABLE / DISABLE SERV_MOD_ACT_TRACE_ENABLE / DISABLE

Statistics subroutines include: CLIENT_ID_STAT_ENABLE / DISABLE SERV_MOD_ACT_STAT_ENABLE / DISABLE

Trace subroutines are equivalent to event 10046 level 8 Include wait events by default

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TraceDBMS_MONITOR - PLAN_STAT column In Oracle 11.1 and above the following subroutines include the PLAN_STAT

column: SESSION_TRACE_ENABLE DATABASE_TRACE_ENABLE CLIENT_ID_TRACE_ENABLE SERV_MOD_ACT_TRACE_ENABLE

PLAN_STAT specifies the dump frequency for row source (STAT) statistics

Values can be: NEVER FIRST_EXECUTION (default) ALL_EXECUTIONS

Useful when individual statement executions are affected by data cardinality / selectivity

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Parameters


ParametersV$PARAMETER V$PARAMETER includes supported parameters

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NUM NUMBER

NAME VARCHAR2(80)

TYPE NUMBER

VALUE VARCHAR2(4000)

DISPLAY_VALUE VARCHAR2(4000)

DEFAULT_VALUE VARCHAR2(255)

ISDEFAULT VARCHAR2(9)

ISSES_MODIFIABLE VARCHAR2(5)

ISSYS_MODIFIABLE VARCHAR2(9)

ISPDB_MODIFIABLE VARCHAR2(5)


IS_INSTANCE_MODIFIABLE VARCHAR2(5)

ISMODIFIED VARCHAR2(10)

ISADJUSTED VARCHAR2(5)

ISDEPRECATED VARCHAR2(5)

ISBASIC VARCHAR2(5)

DESCRIPTION VARCHAR2(256)

UPDATE_COMMENT VARCHAR2(256)

HASH NUMBER

CON_ID NUMBER

CON_ID - new in Oracle 12.1 -> Container ID ISPDB_MODIFIABLE is also new in 12.1


ParametersV$PARAMETER V$PARAMETER includes supported parameters

Based on X$KSPPI - includes all parameters

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Version Supported Unsupported Total

11.2.0.3 348 2403 2751

11.2.0.4 352 2562 2914

12.1.0.1 367 2984 3351

12.1.0.2 381 3597 3978

To set an unsupported parameter use double quotes around name e.g.:

ALTER SESSION SET "_serial_direct_read" = NEVER;

V$PARAMETER includes non-default values for unsupported parameters


ParametersUnsupported parameters V$PARAMETER only reports non-default values for unsupported parameters

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SELECT i.ksppinm||';'||sv.ksppstvl

FROM x$ksppi i, x$ksppsv svWHERE i.indx = sv.indxORDER BY i.ksppinm;

To dump values for all parameters including default parameters for unsupported parameters:


ParametersV$PARAMETER_VALID_VALUES V$PARAMETER_VALID_VALUES - supported parameters

Based on X$KSPVLD_VALUES - all parameters

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Version Supported Unsupported Total

11.2.0.3

11.2.0.4 73 91 164

12.1.0.1 75 112 187

12.1.0.2 78 124 202


NUM NUMBER

NAME VARCHAR2(64)

ORDINAL NUMBER

VALUE VARCHAR2(255)

ISDEFAULT VARCHAR2(64)

CON_ID NUMBER


ParametersV$PARAMETER_VALID_VALUES For example:

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Value Default

ALWAYS FALSE

AUTO FALSE

NEVER FALSE

TRUE FALSE

FALSE FALSE

SELECT value_kspvld_values AS "Value",isdefault_kspvld_values AS "Default"

FROM x$kspvld_valuesWHERE name_kspvld_values = '_serial_direct_read'ORDER BY ordinal_kspvld_values;


Featuresand

Hints


Features and HintsV$SQL_FEATURE Based on X$QKSFM

Includes features and fixes

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SQL_FEATURE VARCHAR2(64)

DESCRIPTION VARCHAR2(64)

PROPERTY NUMBER

Individual fixes can be enabled and disabled. For example:

Fixes can be identified from DESCRIPTION column

WHERE description LIKE 'Fix%'

ALTER SESSION SET "_fix_control"='6776808:off';


Features and HintsV$SQL_FEATURE Version counts are:

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Version0 Feature Fix Total

11.2.0.3 94 654 748

11.2.0.4 98 846 944

12.1.0.1 110 885 996

12.1.0.2 115 1071 1186


Features and HintsV$SQL_FEATURE_HIERARCHY V$SQL_FEATURE describes the relationships between features

The root feature is QKSFM_ALL

The following query prints the hierarchy in a nested format:

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SELECT lpad ( ' ' , level * 2 ,' ' ) || sql_featureFROM v$sql_feature_hierarchyCONNECT BY PRIOR sql_feature = parent_idSTART WITH parent_id = 'QKSFM_ALL';

....

QKSFM_TRANSFORMATIONQKSFM_CBQT

QKSFM_CVMQKSFM_DIST_PLCMTQKSFM_JOINFACQKSFM_JPPDQKSFM_PLACE_GROUP_BYQKSFM_PULL_PRED

....


Features and HintsV$SQL_HINT Based on X$QKSHT

Currently no concept of unsupported hints

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NAME VARCHAR2(64)

SQL_FEATURE VARCHAR2(64)

CLASS VARCHAR2(64)

INVERSE VARCHAR2(64)

TARGET_LEVEL NUMBER

PROPERTY NUMBER

VERSION VARCHAR2(25)

VERSION_OUTLINE VARCHAR2(25)

INVERSE column Describes the opposite hint e.g.: PUSH_PRED and NO_PUSH_PRED

Version # Hints

11.2.0.3 273

11.2.0.4 277

12.1.0.1 314

12.1.0.2 332


Features and HintsV$SQL_HINT VERSION column

Describes version in which hint was introduced:

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Version # New Hints

8.0.0 14

8.1.0 50

8.1.5 18

8.1.6 4

8.1.7 2

9.0.0 26

9.2.0 13

10.1.0.3 42

10.2.0.1 35

10.2.0.2 4

10.2.0.3 3

Version # New Hints

10.2.0.4 2

10.2.0.5 4

11.1.0.6 32

11.1.0.7 5

11.2.0.1 19

11.2.0.2 6

11.2.0.3 6

11.2.0.4 2

12.1.0.1 37

12.1.0.2 18


ExecutionPlans


Execution PlansDBMS_XPLAN - Overview Introduced in Oracle 9.2

Enhanced in subsequent releases

SELECT * FROM TABLE (DBMS_XPLAN.DISPLAY_CURSOR);

Defined in $ORACLE_HOME/rdbms/admin/dbmsxpln.sql

Useful subroutines include DISPLAY - display a plan from a PLAN_TABLE DISPLAY_AWR - display a plan from the AWR DISPLAY_CURSOR - display a plan from the library cache DISPLAY_PLAN – returns plan as a CLOB DISPLAY_SQLSET – displays a plan from a SQL tuning set DISPLAY_SQLPLAN_BASELIN E – displays a plan from SQL baseline

For example to display execution plan for statement most recently executed by the current session:


Execution PlansDBMS_XPLAN - FORMAT Column All DISPLAY subroutines include a FORMAT column which can be:

BASIC Minimum information Display operation ID, name and option

TYPICAL Default. Display operation ID, name and option, #rows, #bytes and optimizer

cost. Includes pruning, parallel and predicate information when applicable

ALL Maximum information As TYPICAL plus projection, alias and remote SQL if applicable

SERIAL Same as TYPICAL except parallel information is not displayed even if

statement executes in parallel

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Execution PlansDBMS_XPLAN - FORMAT Column Options FORMAT column options can be fine-tuned using the following keywords:

ROWS - number of rows estimated by optimizer BYTES - number of bytes estimated by optimizer COST - optimizer cost information PARTITION - partition pruning information PARALLEL - parallel execution information PREDICATE - predicate section PROJECTION - projection section ALIAS - query block name / object alias REMOTE - distributed query information NOTE - note section

If keyword is prefixed by a minus sign then specified information is excluded BASIC ROWS - displays basic information plus number of rows ALL -PROJECTION -NOTE displays everything except the projection and

note sections

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Execution PlansDBMS_XPLAN - Additional Statistics For DISPLAY_CURSOR and DISPLAY_SQLSET, additional data can be output

using the following keywords:

IOSTATS – shows IO statistics for all executions of the cursor MEMSTATS – displays memory management statistics including

execution mode of operator how much memory was used number of bytes spilled to disk

ALLSTATS – both IOSTATS and MEMSTATS LAST – only report statistics for last execution of cursor

IOSTATS, ALLSTATS and LAST require basic plan statistics which are collected by

setting STATISTICS_LEVEL parameter to ALL specifying GATHER_PLAN_STATISTICS hint

MEMSTATS requires PGA memory management to be enabled by: setting PGA_AGGREGATE_TARGET to non-zero value

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Execution PlansOperations and Options AWR includes some interesting (static) views that describe execution plan

operations and options available in the installed database version

DBA_HIST_PLAN_OPERATION_NAME Contains a list of row source operations

DBA_HIST_PLAN_OPTION_NAME Contains a list of row source options

DBA_HIST_TOPLEVELCALL_NAME Contains a list of top level calls Used in DBA_HIST_ACTIVE_SESS_HISTORY

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Events


Event 10046Levels Event 10046 has additional levels in recent versions

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Level Description Version

1 Trace includes SQL statement, response time, service time, execution statistics (#rows, #LIOs #PRs #PWs)In 10.2 and below execution plan written to trace file when associated cursor is closed. In 11.1 and above execution plan written to trace file after first execution of each cursor - plan_stat = 'first_execution'

All

4 As level 1 plus bind varables All

8 As level 1 plus wait times All

16 As level 1 plus execution plans for every executionplan_stat = 'all_executions'

11.1 and above

32 As level 1 without any execution plansplan_stat = 'never'

11.1 and above

64 As level 1 plus execution plans for any statement execution requiring more than 60 seconds of DB time

11.2.0.2 and above


Event 10046Bind Variables Event 10046 level 4 trace only captures the first bind variable in array

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EXECUTE dbms_monitor.session_trace_enable (binds=>TRUE);

CREATE TABLE driver (key VARCHAR2(4), name VARCHAR2(30));

DECLARE TYPE driver_tab IS TABLE OF driver%ROWTYPE; d driver_tab := driver_tab ();BEGIN d.extend (6); d(1).key := 'LHAM'; d(1).name := 'Lewis Hamilton'; d(2).key := 'NROS'; d(2).name := 'Nico Rosberg'; d(3).key := 'SVET'; d(3).name := 'Sebastian Vettel'; d(4).key := 'FALO'; d(4).name := 'Fernando Alonso'; d(5).key := 'DRIC'; d(5).name := 'Daniel Ricciardo'; d(6).key := 'JBUT'; d(6).name := 'Jenson Button';

FORALL j IN 1..3INSERT INTO driver VALUES (d(j).key,d(j).name);

FORALL j IN 4..6INSERT INTO driver VALUES (d(j).key,d(j).name);

END;


Event 10046Bind Variables Trace will only contain bind variable values for two rows:

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BINDS #139676743602632:Bind#0

...value="LHAM"

Bind#1...value="Lewis Hamilton"

...

BINDS #139676743602632:Bind#0

...value="FALO"

Bind#1...value="Fernando Alonso"

Trace only includes first row of each array insert Remaining rows are not traced

Note this issue has consequences for load generation / simulation tools such as HammerDB and LoadRunner which base their input on 10046 trace.


Event 10053Optimizer Decisions To trace optimizer decisions use enable event 10053:

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Level Description Version

1 Print statistics and computations All

2 Print computations only All

Details are only written to trace when the statement is hard-parsed


Event 10053 DBMS_SQLDIAG Provides APIs to diagnose SQL statements.

Used by diagnostic modules: SQL_TESTCASE SQL_DIAGNOSTIC

Defined in $ORACLE_HOME/rdbms/admin/dbmsdiag.sql

Includes DUMP_TRACE procedure: Dumps 10053 trace (optimizer or compiler) trace for a specific SQL

statement Does not execute SQL statement to generate trace Compiler trace is a superset of optimizer trace

Includes kkf library calls Query block decisions Expressions

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Event 10053 DBMS_SQLDIAG DUMP_TRACE procedure parameters are:

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Name Description

p_sql_id Child cursor SQL_ID

p_child_number Child cursor number

p_component "Optimizer" or "Compiler"

p_file_id tracefile_identifier

For example:

dbms_sqldiag.dump_trace(

p_sql_id => '2y220pbrk573n',p_child_number => 0,p_component => 'Optimizer',p_file_id => 'OPTIMIZER'

);

Note that P_FILE_ID sets TRACEFILE_IDENTIFIER, but does not reset it at end of call so subsequent trace file be written to the new file. Alternatively NULL can be specified (the default)


ORADEBUG


ORADEBUGIntroduction Undocumented debugging utility available

as a standalone utility on Unix (oradbx) as a standalone utility on VMS (orambx) within Server Manager (svrmgr) within SQL*Plus (8.1.5 and above)

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SQL> ORADEBUG HELP

Requires SYSDBA privilege

Options vary for each release

To list available options use:


ORADEBUGProcess Specification There are four ways of specifying a process in ORADEBUG:

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SQL> ORADEBUG SETMYPID

Using Oracle PID (V$PROCESS.PID)

Using the Oracle process name:

For example:

SQL> ORADEBUG SETORAPID <pid>

Using operating system PID (V$PROCESS.SPID)

SQL> ORADEBUG SETOSPID <spid>

SQL> ORADEBUG SETORAPNAME <pname>

SQL> ORADEBUG SETORAPNAME PMON

Using current process:


ORADEBUGUseful Commands To display the current trace file name use:

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SQL> ORADEBUG TRACEFILE_NAME

To flush the current trace file use:

SQL> ORADEBUG FLUSH

To set the maximum size of the current trace file to UNLIMITED use:

SQL> ORADEBUG UNLIMIT

SQL> ORADEBUG SETTRACEFILEID <suffix>

To set the TRACEFILE_IDENTIFER parameter:

To dump the currently executing statement (SQL or PL/SQL)

SQL> ORADEBUG CURRENT_SQL


ORADEBUGDumps Dumps vary for each release:

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SQL> ORADEBUG DUMPLIST

To list available dumps:

To perform an dump immediately use:

SQL> ORADEBUG DUMP <dump_name> <level> [address]

To perform a dump periodically use:

SQL> ORADEBUG PDUMP [interval=<interval>] [ndumps=<count> <dump_name> <level> [address]


ORADEBUGProcess Statistics To dump process statistics use ORADEBUG PROCSTAT. For example:

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SQL> ORADEBUG SETORAPNAME PMONSQL> ORADEBUG PROCSTAT

----- Dump of Process Statistics -----User time used = 65System time used = 30Maximum resident set size = 28452Integral shared text size = 0Integral unshared data size = 0Integral unshared stack size = 0Page reclaims = 7480Page faults = 7Swaps = 0Block input operations = 1472Block output operations = 32Socket messages sent = 0Socket messages received = 0Signals received = 0Voluntary context switches = 2555Involuntary context switches = 387


ORADEBUGComponents ORADEBUG includes internal documentation for

Components Events

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SQL> ORADEBUG DOC

Internal Documentation

EVENT Help on events (syntax, event list, ...)

COMPONENT [<comp_name>] List all components or describe <comp_name>

Components are arranged in nested hierarchies Each component has a unique name Do not need to specify parent(s) to uniquely identify component

Most component descriptions include the internal module name(s) e.g.:

SQL_Execution SQL Execution (qer, qes, kx, qee)

Parallel_Execution Parallel Execution (qerpx, qertq, kxfr, kxfx, kxfq, kxfp)


ORADEBUGComponents Components are grouped into eight libraries:

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Library Description

ADVCMP Advanced Compression

CLIENT Client

DIAG Diagnostics

GENERIC Numeric Events

LIBCELL Exadata Cells

ORANET Networking

PLSQL PL/SQL

RDBMS RDBMS


ORADEBUGComponents For example given the extract below from ORADEBUG DOC COMPONENT:

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Components in library RDBMS:

SQL_Compiler SQL Compiler ((null))SQL_Parser SQL Parser (qcs)SQL_Semantic SQL Semantic Analysis (kkm)SQL_Optimizer SQL Optimizer ((null))

SQL_Transform SQL Transformation (kkq, vop, nso)SQL_MVRW SQL Materialized View Rewrite ((null))SQL_Vmerge SQL View Merging (kkqvm)SQL_Virtual SQL Virtual Column (qksvc, kkfi)

SQL_APA SQL Access Path Analysis (apa)SQL_Costing SQL Cost-based Analysis (kko, kke)

SQL> ORADEBUG DOC RDBMSSQL> ORADEBUG DOC SQL_CompilerSQL> ORADEBUG DOC SQL_OptimizerSQL> ORADEBUG DOC SQL_TransformSQL> ORADEBUG DOC SQL_Vmerge

The following are all valid:


ORADEBUGEvents The full event syntax is described in ORADEBUG:

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SQL> ORADEBUG DOC EVENT

<event_spec>::= '<event_id> [<event_scope>][<event_filter_list>][<event_parameters>][<action_list>][off]'

<event_id> ::= <event_name | number>[<target_parameters>]

<event_scope> ::= [<scope_name>: scope_parameters]

<event_filter> ::= {<filter_name>: filter_parameters}

<action> ::= <action_name>(action_parameters)

<*_parameters> ::= <parameter_name> = <value>[, ]


ORADEBUGEvents Each event specification is comprised of up to four parts:

Name Scope Filter Action

Not all of the above are always required Defaults apply for many permutations

More information is available in:

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SQL> ORADEBUG DOC EVENT NAME

SQL> ORADEBUG DOC EVENT SCOPE

SQL> ORADEBUG DOC EVENT FILTER

SQL> ORADEBUG DOC EVENT ACTION


ORADEBUGEvents - Name Event names are optional:

Can be specified for some libraries

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Name Description

alert_text event for textual alerts

trace_recursive force tracing of recursive SQL statements

clientid_overwrite overwrite client_identifier in client_info

sql_monitor force monitoring of SQL statements

sql_trace sql trace

pmon_startup startup of pmon process

background_startup startup of background processes

db_open_begin start of database open operation

For example for the RDBMS library:


ORADEBUGEvents - Scope Scope is the SQL scope for RDBMS events

Defined using SQL[ ]

Syntax is

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[SQL: sql_id <string> ]

For example:

[SQL: 3s1yukp05bzg6]

Multiple SQL_IDs can be specified using | as a separator

[SQL: 3s1yukp05bzg6 | aca4xvmz0rzup]


ORADEBUGEvents - Filter Filters include:

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Library Filter Description

DIAG occurence Fire events after specified number of occurrences

DIAG callstack Fire events when specified function is on stack

DIAG tag Fire events when specified tag is set

RDBMS process Fire events for specific process

RDBMS pgadep Fire when pgadep is within specified range

GENERIC errarg Fire events for specific error argument

Filters must be enclosed in curly brackets. For example pgadep below:

SQL> ALTER SESSION SET EVENTS

'sql_trace[SQL: 32cqz71gd8wy3] {pgadep: exactdepth 0}

plan_stat=all_executions,wait=true,bind=true';


ORADEBUGEvents - Filter pgadep is the PGA depth (dep=N) in trace file.

Can take the following values: exactDepth lessThan greaterThan

For example:

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{pgadep: exactdepth 0}

For normal statement execution dep = 0 SQL statement execution

For PL/SQL execution dep = 0 PL/SQL execution dep = 1 SQL statement execution


ORADEBUGEvents - Action Actions exist for each library (except PLSQL)

For the RDBMS library most actions correspond to ORADEBUG DUMP commands from older versions including:

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Dump Name Description

PROCESSSTATE Dump process state

SYSTEMSTATE Dump system state

HEAPDUMP Dump memory heap

GLOBAL_AREA Dump fixed global area(s)

BUFFERS Dump all buffers in buffer cache

SET_TSN_P1 Set tablespace # for buffer dump

BUFFER Dump all buffers for specific DBA

LIBRARY_CACHE Dump the library cache

CURSORDUMP Dump session cursors


ORADEBUGEvents - SQL_TRACE

SQL_TRACE is an synonym for event 10046 and can be set using: ORADEBUG ALTER SYSTEM ALTER SESSION

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SQL> ORADEBUG DOC EVENT NAME SQL_TRACE

sql_trace: event for sql trace

Usage

sql_trace wait < false | true >, bind < false | true >, plan_stat < never | first_execution | all_executions | adaptive >, level <ub4>

The ORADEBUG syntax is:

The default level is 1


ORADEBUGEvents - SQL_TRACE For example:

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ORADEBUG EVENT SQL_TRACE

ORADEBUG EVENT SQL_TRACE BIND=TRUE

ORADEBUG EVENT SQL_TRACE BIND=TRUE,WAIT=TRUE

ORADEBUG EVENT SQL_TRACE OFF

ORADEBUG EVENT SQL_TRACE PLAN_STAT=ALL_EXECUTIONS

ORADEBUG EVENT SQL_TRACE LEVEL=4


ORADEBUGEvents - Examples Numeric events can be set using ORADEBUG. Default level is 1

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ORADEBUG EVENT 10053

ORADEBUG EVENT 10053 TRACE NAME CONTEXT FOREVER, LEVEL 1

ORADEBUG EVENT 10053 TRACE NAME CONTEXT OFF

ORADEBUG EVENT 10053 LEVEL 1

ORADEBUG EVENT 10053 OFF

The original syntax still works in Oracle 11g/12c


ALTERStatements


ALTER StatementsSQL_TRACE In all versions SQL_TRACE can be enabled using ALTER SESSION/SYSTEM

Examples shown for ALTER SESSION:

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SQL> ALTER SESSION SET SQL_TRACE=TRUE;

In Oracle 11.1 and above SQL_TRACE is an event:

SQL> ALTER SESSION SET EVENTS 'sql_trace wait=true';

SQL> ALTER SESSION SET EVENTS 'sql_trace bind=true';

SQL> ALTER SESSION SET EVENTS 'sql_trace bind=true, wait=true';

SQL> ALTER SESSION SET EVENTS 'sql_trace plan_stat=all_executions';


ALTER StatementsNumeric Events Numeric events can still be set using ALTER SESSION / ALTER SYSTEM

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SQL> ALTER SESSION SET EVENTS '10235 level 1';

SQL> ALTER SESSION SET EVENTS '10235 off';

SQL> ALTER SESSION SET EVENTS '10235';

SQL> ALTER SESSION SET EVENTS '10235 trace name context forever, level 1';

SQL> ALTER SESSION SET EVENTS '10235 trace name context off';

The original syntax still works in Oracle 11g/12c


ALTER StatementsSQL_TRACE - Filter Trace can be restricted to a specific SQL ID by specifying a filter:

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SQL> ALTER SESSION SET EVENTS 'sql_trace [sql: sql_id=3s1yukp05bzg6] bind=true, wait=true';

SQL> ALTER SESSION SET EVENTS 'sql_trace [sql: sql_id=3s1yukp05bzg6|aca4xvmz0rzup] bind=true, wait=true';

Multiple SQL IDs can be specified using the | symbol as a separator


ALTER Statements TRACE - Components Trace can be restricted to a specific components e.g.

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SQL> ALTER SESSION SET EVENTS 'trace[rdbms.SQL_Optimizer.*]';

SQL> ALTER SESSION SET EVENTS 'trace[SQL_Optimizer.*][sql:3bnxc7htmf2ad]';

Individual components can also be filtered e.g.:

The library name can optionally be omitted e.g.

SQL> ALTER SESSION SET EVENTS 'trace[SQL_Optimizer.*]';

Disable trace again using:

SQL> ALTER SESSION SET EVENTS 'trace[SQL_Optimizer.*] off';


ALTER StatementsFlushing Caches To flush the buffer cache use:

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ALTER SYSTEM FLUSH BUFFER_CACHE;

ALTER SYSTEM FLUSH SHARED_POOL;

The buffer cache must be flushed to disk before attempting to dump blocks using the ALTER SYSTEM DUMP command

To flush the shared pool (library cache) use:

Pinned objects will not be flushed


ALTER StatementsBlock Dumps To dump a database block in Oracle 8.0 or above:

ALTER SYSTEM DUMP DATAFILE <absolute_file_number>BLOCK <block_number>;

ALTER SYSTEM DUMP DATAFILE <absolute_file_number>BLOCK MIN <minimum_block_number>BLOCK MAX <maximum_block_number>;

To dump a range of database blocks:

To dump a block from a datafile in a closed database:

ALTER SYSTEM DUMP DATAFILE '<file_name>'BLOCK <block_number>;


ALTER StatementsBlock Dumps In Oracle 12c ASSM bitmap blocks cannot be dumped by default

Block is considered to be encrypted

Work around is to set

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ALTER SESSION SET "_sga_clear_dump" = TRUE;

Acknowledgements to Jonathan Lewis and Riyaj Shamsudeen for the above

X$KSPPI description for this parameter is:

Allow dumping encrypted blocks in clear for debugging


ALTER StatementsRedo Log Dumps To identify the current redo log use:

SELECT member FROM v$logfileWHERE group# = (

SELECT group# FROM v$logWHERE status = 'CURRENT'

);

To dump the contents of a redo log use:

ALTER SYSTEM DUMP LOGFILE '<logfilename>';

Also works for archived log files


ALTER StatementsRedo Log Dumps Full syntax is:

ALTER SYSTEM DUMP LOGFILE 'FileName' SCN MIN MinimumSCN SCN MAX MaximumSCN TIME MIN MinimumTime TIME MAX MaximumTime LAYER Layer OPCODE Opcode DBA MIN FileNumber . BlockNumber DBA MAX FileNumber . BlockNumber RBA MIN LogFileSequenceNumber . BlockNumber RBA MAX LogFileSequenceNumber . BlockNumber;

See MOS Note 1031381.6 for further details


Thank You For Your Interest

Please send any questions or comments to:

[email protected]

1 © 2014 Julian Dyke juliandyke.com Advanced Diagnostics Revisited Julian Dyke Independent...

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