Oracle Internals之Dumps

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Dumps

Immediate Dumps

Conditional Dumps

Memory Dumps

File Dumps

Immediate Dumps

There are three ways of specifying an immediate dump

Immediate dumps can be specified using the ALTER SESSION command

ALTER SESSION SET EVENTS

'immediate trace name dump levellevel';

Immediate dumps can be specified in ORADEBUG

ORADEBUG DUMP dump level

Immediate dumps can also be specified using the DBMS_SYSTEM.SET_EV procedure

EXECUTE dbms_system.set_ev (sid,serial#,65535,level,'dump');

Immediate dumps cannot be invoked from init.ora

Conditional Dumps

Conditional dumps are invoked when an error occurs

Conditional dump can be specified in the init.ora file e.g

event="error trace name dump levellevel"

Conditional dumps can be specified in the current session

ALTER SESSION SET EVENTS

'error trace name dump levellevel';

Conditional dumps can be specified in ORADEBUG

ORADEBUG EVENT error trace namedump level level

ORADEBUG SESSION_EVENT error trace namedump level level

Memory Dumps

Dumping the Global Area

The following command can be used to dump the global area

ALTER SESSION SET EVENTS 'immediate trace name global_area levellevel';

Levels are (bitmask)

Level

Description

Include PGA

Include SGA

Include UGA

Include indirect memory dumps

The following ORADEBUG command has the same effect

ORADEBUG DUMP GLOBAL_AREA level

The structure of the fixed SGA is externalised in X$KSMFSV

Name

Type

Description

ADDR

RAW(4)

INDX

NUMBER

INST_ID

NUMBER

KSMFSNAM

VARCHAR2(64)

Name

KSMFSTYP

VARCHAR2(64)

Type

KSMFSADR

RAW(4)

Address

KSMFSSIZ

NUMBER

Size in Bytes

This can be queried using

SELECT

SUBSTR (ksmfsnam,1,20) AS "Name",

SUBSTR (ksmfstyp,1,20) AS "Type",

ksmfsadr AS "Address",

ksmfssiz AS "Size"

FROM x$ksmfsv;

Dumping the Library Cache

The following command can be used to dump the library cache

ALTER SESSION SET EVENTS 'immediate trace name library_cache levellevel';

where level is one of the following

Level

Description

Dump library cache statistics

Include hash table histogram

Include dump of object handles

Include dump of object structures (heap 0)

For example

ALTER SESSION SET EVENTS 'immediate trace name library_cache level 1';

The following ORADEBUG command has the same effect

ORADEBUG DUMP LIBRARY_CACHE level

Dumping the Row (Dictionary) Cache

ROW_CACHE

The row cache is also known as the dictionary cache

The following command can be used to dump the row cache

    ALTER SESSION SET EVENTS 'immediate trace name row_cache level level';

where level is one of the following

Level

Description

Dump row cache statistics

Include hash table histogram

Include dump of object structures

For example

    ALTER SESSION SET EVENTS 'immediate trace name row_cache level 1';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP ROW_CACHE level

Dumping Multiple Buffers

Multiple Buffers

To dump buffer headers and buffer contents for buffers currently in the cache

    ALTER SESSION SET EVENTS 'immediate trace name buffers level level';

where level is one of the following

Level

Description

Buffer headers only

Level 1 + block headers

Level 2 + block contents

Buffer headers only + hash chain

Level 1 + block headers + hash chain

Level 2 + block contents + hash chain

Buffer headers only + hash chain + users/waiters

Level 1 + block headers + hash chain + users/waiters

Level 2 + block contents + hash chain + users/waiters

Dumping Individual Buffers

Individual Buffers

In Oracle 8.0 and above is is possible to dump buffer all buffers currently in the cache for a specific block

For example where a block has been modified and is subject to consistent read from a number of transactions, there may be more than one copy of the block in the buffer cache

First identify（确定，定位，指定） the tablespace number for the block e.g for tablespace TS01

    SELECT ts# FROM sys.ts$

    WHERE name = 'TS01';

Set the tablespace number using

    ALTER SESSION SET EVENTS

    'immediate trace name set_tsn_p1 level level';          //

where level is the tablespace number + 1

Identify （确定，定位，指定）the relative DBA for the block

This is equal to

    RelativeFileNumber * 4194304 + BlockNumber

e.g. for a block with relative file number of 5 and a block number of 127874

    5 * 4194304 + 127874 = 21099394

Dump the buffer using

    ALTER SESSION SET EVENTS

    'immediate trace name buffer level level';

where level is therelative DBA e.g.

    ALTER SESSION SET EVENTS

    'immediate trace name buffer level 21099394';注释： ALTER SESSION SET EVENTS 
    'immediate trace name set_tsn_p1 level level';  和ALTER SESSION SET EVENTS
    'immediate trace name buffer level 21099394';
这两句话要联合起来使用，才能把一个指定的数据块的内容给转存出来。
也就是说，dump（转存）一个指定的数据块的内容时，要将该数据块所在的表空间的表空间号提供给负责执行dump（转存）的进程（通过使用第一句话），之后，负责执行dump（转存）的进程还得知道该数据块的RDBA是多少（通过使用第二句话），这样，负责执行dump（转存）的进程就可以锁定（或说找到）该数据块的具体位置从而将其内容转存出来。这里，说明一点，RDBA里使用的是相对文件号（RelativeFileNumber），相对文件号（RelativeFileNumber）是给在一个表空间范围里的文件进行的编号，DBA里使用的是绝对文件号（absoluteFileNumber，简称FileNumber），绝对文件号（absoluteFileNumber，简称FileNumber）是给在一个数据库范围里的文件进行的编号。

Dumping Memory Heaps

Memory Heaps

To dump the top-level heap in a memory area

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump level level';

Levels are

Level

Description

PGA summary

SGA summary

UGA summary

Callheap (Current)

Callheap (User)

Large pool

Streams pool

128

Java pool

1025

PGA with contents

2050

SGA with contents

4100

UGA with contents

8200

Callheap with contents (Current)

16400

Callheap with contents (User)

32800

Large pool with contents

65600

Streams pool with contents

131200

Java pool with contents

Levels are correct to Oracle 10.2.0.1

The levels can be combined. For example a level 3 dump will contain both the PGA and SGA

Dumping Memory Subheaps

Memory Subheaps

Each heap may have one or more subheaps. These can be dumped using the command

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump_addr level level';

where the level is the address of the subheap.

The syntax for this command changed in Oracle 9.2

Oracle 9.0.1 and below

Oracle 9.2.0 and above

Oracle 9.0.1 and below

For Oracle 9.0.1 and below a summary dump is obtained by setting the level to the decimal value of the address. A detailed dump is obtained by adding 1 to the decimal value of the address.

For example to dump the subheap at address 0x8057eb78, first convert the address to decimal (2153245560)

The subheap address can be found in the heapdump, for example

    ds=0x8057eb78

For a summary dump use

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump_addr level 2153245560';

For a detailed dump, add 1 to the address e.g.

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump_addr level 2153245561';

Oracle 9.2.0 and above

In Oracle 9.2 and above, for a summary dump

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump_addr level 1, addr 2153245560';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP HEAPDUMP_ADDR 1 2153245560

In Oracle 9.2 and above, for a detailed dump

    ALTER SESSION SET EVENTS

    'immediate trace name heapdump_addr level 2, addr 2153245560';

Note that in Oracle 9.2 it is no longer necessary to add 1 to the address

The following ORADEBUG command has the same effect

    ORADEBUG DUMP HEAPDUMP_ADDR 2 2153245560

Dumping Process State

Process State

To dump the process state use:

    ALTER SESSION SET EVENTS

    'immediate trace name processstate level level';

For example

    ALTER SESSION SET EVENTS 'immediate trace name processstate level 10';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP PROCESSSTATE level

The amount of library cache dump output for state object dumps can be limited using event 10065

Dumping System State

System State

A system state dump contains the process state for every process.

Every state object for every process is dumped.

A state object represents the state of a database resource including

processes
sessions
enqueues (locks)
buffers

State objects are held in the SGA

A system state dump does not represent a snapshot of the instance because the database is not frozen for the duration of the dump. The start point of the dump will be earlier than the end point.

Oracle recommends the use of system state dumps to diagnose

hanging databases
slow databases
database errors
waiting processes
blocking processes
resource contention

To dump the system state use

    ALTER SESSION SET EVENTS

    'immediate trace name systemstate level level';

For example

    ALTER SESSION SET EVENTS 'immediate trace name systemstate level 10';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP SYSTEMSTATE level

A system state dump can be triggered by an error, for example the following init.ora parameter

    event = "60 trace name systemstate level 10"

will generate a systemstate dump whenever a deadlock is detected (ORA-00060)

The amount of library cache dump output for state object dumps can be limited using event 10065

Dumping the Error Stack

Error Stack

An error stack describes the current state of a process. It includes the current SQL statement and the process state for the process.

Oracle recommends taking an error stack dump to diagnose

what the process is doing
a problem identified by a systemstate dump
processes looping or hanging

Error stack dumps can also be triggered by an error

To dump an error stack use

    ALTER SESSION SET EVENTS

    'immediate trace name errorstack level level';

where level is one of the following

Level

Description

Error stack only

Error stack and function call stack

As level 1 plus the process state

As level 2 plus the context area

The following ORADEBUG command has the same effect

    ORADEBUG DUMP ERRORSTACK level

An alternative syntax for the same command is

    ORADEBUG EVENT IMMEDIATE TRACE NAME ERRORSTACK level

To dump a level 3 errorstack when ORA-00942 (table or view does not exist) use

    ALTER SESSION SET EVENTS

    '942 trace name errorstack level 3';

A conditional errorstack dump can also be specified without a level e.g.

    ALTER SESSION SET EVENTS

    '604 trace name errorstack';

Alternatively a conditional errorstack dump can be specified in the init.ora file

    event = "942 trace name errorstack level 3"

Errorstacks can also be dumped conditionally using ORADEBUG

    ORADEBUG EVENT 942 TRACE NAME ERRORSTACK LEVEL 3

A level 3 errorstack contains the following sections

Call Stack Trace

Files Currently Opened

Process State

Pinned Buffer History

Cursor Dump

Fixed PGA

Fixed SGA

Fixed UGA

In memory trace dump

Dumping Hang Analysis

Hang Analysis

This dump is available in Oracle 8.0.6 and Oracle 8.1.6 and above. It is not available in Oracle 8.1.5.

It contains

systemstate level 1 dump
processes currently waiting, blocking or spinning
errorstacks

The HANGANALYZE dump is more selective than a SYSTEMSTATE dump in that it only includes details of processes of interest. It is particularly intended for situations where a database is hanging.

For example

    ALTER SESSION SET EVENTS

    'immediate trace name hanganalyze level 5';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP HANGANALYZE level

e.g.

    ORADEBUG DUMP HANGANALYZE 5

A HANGANALYZE dump can also be generated on an error e.g. when a deadlock is detected (ORA-00060) using the init.ora file

    event = "60 trace name hanganalyze level 5"

or in the current session using

    ALTER SESSION SET EVENTS

    '60 trace name hanganalyze level 5';

Dumping Work Areas

Work Areas

To dump the current workareas use

    ALTER SESSION SET EVENTS 'immediate trace name workareatab_dump level level';

Levels are (bitmask)

Level

Description

Global SGA Info

Workarea Table (Summary)

Workarea Table (Detail)

The following ORADEBUG command has the same effect

    ORADEBUG DUMP WORKAREATAB_DUMP level

Dumping Enqueues

Enqueues

To dump the current enqueue states use

    ALTER SESSION SET EVENTS 'immediate trace name enqueues level level';

Levels are

Level

Description

Dump a summary of active resources and locks, the resource free list and the hash table

Include a dump of resource structures

Include a dump of lock structures

The following ORADEBUG command has the same effect

    ORADEBUG DUMP ENQUEUES level

Dumping Latches

Latches

To dump the current latch status use

    ALTER SESSION SET EVENTS 'immediate trace name latches level level';

Levels are

Level

Description

Latches

Include statistics

The following ORADEBUG command has the same effect

    ORADEBUG DUMP LATCHES level

Dumping Events

Events

To dump the events set for the current session

    ALTER SESSION SET EVENTS 'immediate trace name events level level';

Levels are

Level

Description

Session

Process

System

The following ORADEBUG command has the same effect

    ORADEBUG DUMP EVENTS level

Dumping Shared Server (MTS) Processes

Shared Server (MTS) Processes

To dump buffer headers and buffer contents for buffers currently in the cache

    ALTER SESSION SET EVENTS 'immediate trace name shared_server_state level level';

where level is in the range 1 to 14

The following ORADEBUG command has the same effect

    ORADEBUG DUMP SHARED_SERVER_STATE level

In Oracle 8.1.7 and below, this dump is called MTSSTATE

Dumping Background Messages

Background process messages can be traced using

    ALTER SESSION SET EVENTS

    'immediate trace name bg_messages level level';

where level identifies the background process (+1)

For example to find the level of SMON, first identify the index number using the following query

    SELECT indx + 1 FROM x$ksbdp

    WHERE ksbdpnam = 'SMON';

The following ORADEBUG command has the same effect

    ORADEBUG DUMP BG_MESSAGES level

File Dumps

Dumping Columns

Columns

To dump the internal representation of columns use the DUMP built-in function

    DUMP (column_value, format)

where format is

Format

Description

Octal

Decimal

Hexadecimal

Single Character

For example

    SELECT DUMP (1001,16) FROM dual;

returns

    Typ=2 Len=3: c2,b,2

To output a column in hexadecimal use the 'XXXXXXXX' format mask e.g.

    SELECT TO_CHAR (65536,'XXXXXXXX') FROM dual;

returns

Dumping Database Blocks

Database Blocks

The syntax used for dumping database blocks changed when Oracle8 was introduced

Oracle7 and below

Oracle8 and above

Oracle 7 and below

In Oracle7, blocks are identified by a file number and a block number. These must be converted into a data block address. The block can then be dumped using the ALTER SESSION command.

    COLUMN decimalDBA new_value decimalDBA

    SELECT

        dbms_utility.make_data_block_address (&file,&block) decimalDBA

    FROM dual;

    ALTER SESSION SET EVENTS

    'immediate trace name blockdump level &decimalDBA';

Oracle 8 and above

In Oracle8 and above, blocks are uniquely identified by an absolute file number and a block number. The syntax of the ALTER SYSTEM command has been extended to include block dumps

To dump a block

    ALTER SYSTEM DUMP DATAFILE absolute_file_number

    BLOCK block_number;

To dump a range of blocks

    ALTER SYSTEM DUMP DATAFILE absolute_file_number

    BLOCK MIN minimum_block_number

    BLOCK MAX maximum_block_number;

The DATAFILE clause can specify an absolute file number of a datafile name. If the DATAFILE clause specifies a datafile name, the blocks can also be dumped from a closed database e.g.

    ALTER SYSTEM DUMP DATAFILE 'file_name'

    BLOCK block_number;

Normally a symbolic block dump is output. However, this may not be possible if the block has become corrupt. It is possible to output the block dump in hexadecimal.

To dump a block in hexadecimal, enable event 10289

    ALTER SESSION SET EVENTS

    '10289 trace name context forever, level 1';

dump the block(s) using one of the above commands and then disable 10289 again using

    ALTER SESSION SET EVENTS

    '10289 trace name context off';

On Unix systems blocks can also be dumped using theod utility.

    dd bs=8k if=filename skip=200 count=4 | od -x

where

bs is the Oracle block size e.g. 8k
if is the datafile name
skip is the number of blocks to skip from the start of the file
count is the number of blocks to dump

As blocks are written back to the datafiles asynchronously by DBWR, it is possible that changed blocks have not been written back to the disk when they are dumped using operating system utilities.

The probability that a block has been written back to disk can be increased by performing a checkpoint using

    ALTER SYSTEM CHECKPOINT;

or a logfile switch using

    ALTER SYSTEM SWITCH LOGFILE;

Dumping Indexes

Index Tree Dumps

An index tree can be dumped using

    ALTER SESSION SET EVENTS 'immediate trace name treedump level object_id';

where object_id is the object number of the index (in DBA_OBJECTS)

The tree dump includes

branch block headers
leaf block headers
contents of leaf blocks

The following ORADEBUG command has the same effect

    ORADEBUG DUMP TREEDUMP object_id

In Oracle 9.2 a treedump may crash if the index has been created by a primary / unique constraint e.g.

    CREATE TABLE t1 (c1 NUMBER PRIMARY KEY);

    CREATE TABLE t1 (c1 NUMBER);

    ALTER TABLE t1

    ADD CONSTRAINT t1pk PRIMARY KEY (c1);

The treedump crashes when ind$.property > 256

This problem can be prevented by creating the index before creating the constraint

Dumping Undo Segment Headers

Undo Headers

To dump an undo segment header use the command function

    ALTER SYSTEM DUMP UNDO_HEADER 'segment_name';

In Oracle 9.0.1 and above, if system managed undo is enabled, the segment name has to be in double quotes and upper case. This is because there is a leading underscore in the segment name.

A list of undo segment IDs and names can be obtained using

    SELECT segment_id, segment_name

    FROM dba_rollback_segs

    ORDER BY segment_id;

Dumping Undo Blocks

Undo Blocks

To dump an undo block use the equivalent datafile block dump command

For example to dump an undo block in Oracle8 and above use

ALTER SYSTEM DUMP DATABASEabsolute_file_number BLOCK block_number;

Dumping Undo for a Transaction

Undo for a Transaction

To dump all the undo written for a specific transaction, first identify the transaction ID using

    SELECT xidusn, xidslot, xidsqn

    FROM v$transaction;

Dump the undo using the transaction ID

    ALTER SYSTEM DUMP UNDO BLOCK 'segment_name'

    XID xidusn xidslot xidsqn;

Dumping File Headers

To dump all the datafile headers use

ALTER SESSION SET EVENTS 'immediate trace name file_hdrs levellevel';

Levels (circa Oracle 8.1.5) are

Level

Description

Dump datafile entry from control file

Level 1 + generic file header

Level 2 + datafile header

Same as level 3

In later versions, level 7 appears to generate additional trace

The following ORADEBUG command has the same effect

ORADEBUG DUMP FILE_HDRS level

Dumping Control Files

Controlfiles

To dump the current latch status use

    ALTER SESSION SET EVENTS 'immediate trace name controlf level level';

Levels (circa Oracle 8.1.5) are

Level

Description

Generic file header

Level 1 + database information + checkpoint progress records

Level 2 + reuse record section

Same as level 3

In later versions, level 15 appears to generate additional trace

The following ORADEBUG command has the same effect

    ORADEBUG DUMP CONTROLF level

Dumping Redo Log Headers

Redo Log Headers

To dump the redo log headers

    ALTER SESSION SET EVENTS 'immediate trace name redohdr level 1';

Levels (circa Oracle 8.1.5) are

Level

Description

Dump redo log entry from control file

Level 1 + generic file header

Level 2 + log file header

Same as level 3

The following ORADEBUG command has the same effect

    ORADEBUG DUMP REDOHDR level

Dumping Redo Logs

Redo Logs

To identify the current redo log use

    SELECT member FROM v$logfile

    WHERE group# =

    (  SELECT group# FROM v$log

        WHERE status = 'CURRENT'

);

To dump a redo log file use

    ALTER SYSTEM DUMP LOGFILE 'FileName';

e.g.

    ALTER SYSTEM DUMP LOGFILE 'R:/Oracle/Oradata/JD92001/Redo01.log';

The syntax of this statement is as follows

    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;

The minimum and maximum SCN is a decimal number

The minimum and maximum time is a decimal number representing the number of seconds since midnight 01Jan1988. These are calculated using the following formula

    time = (((((yyyy - 1988)) * 12 + mm - 1) * 31 + dd - 1) * 24 + hh) *

           60 + mi) * 60 + ss;

yyyy

Year

&nbsp

month

01-12

day

01-31

hour

00-23

minute

00-59

second

00-59

where

This is the same formula that is used to represent time within the redo log

The layer and opcode are those used to indicate specific operations within the redo log e.g. LAYER 5 OPCODE 4 is an undo segment header commit operation

Note that there must be spaces around the periods in the DBA and RBA.

See Metalink Note 1031381.6 for further examples

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