OracleInternals之Dumps

Immediate Dumps

Conditional Dumps

Memory Dumps

File 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 level level';

Levels are (bitmask)

The following ORADEBUG command has the same effect

ORADEBUG DUMP GLOBAL_AREA level

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

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 level level';

where level is one of the following

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

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

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 the relative 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

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

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

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 divs

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)

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

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

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

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

Dumping Columns

Columns

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

    DUMP (column_value, format)

where format is

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

    10000

Dumping Database Blocks

Database Blocks

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

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 the od 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);

or

    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 DATABASE absolute_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 level level';

Levels (circa Oracle 8.1.5) are

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

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

The following ORADEBUG command has the same effect

    ORADEBUG DUMP REDOHDR level

Dumping Redo Logs

yyyy

Year

mm

month

01-12

dd

day

01-31

hh

hour

00-23

mi

minute

00-59

ss

second

00-59