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PT-VARIABLE-ADVISOR(1)User Contributed Perl DocumentatioPT-VARIABLE-ADVISOR(1)

NAME
       pt-variable-advisor - Analyze MySQL variables and advise	on possible
       problems.

SYNOPSIS
       Usage: pt-variable-advisor [OPTIONS] [DSN]

       pt-variable-advisor analyzes variables and advises on possible
       problems.

       Get SHOW	VARIABLES from localhost:

	 pt-variable-advisor localhost

       Get SHOW	VARIABLES output saved in vars.txt:

	 pt-variable-advisor --source-of-variables vars.txt

RISKS
       Percona Toolkit is mature, proven in the	real world, and	well tested,
       but all database	tools can pose a risk to the system and	the database
       server.	Before using this tool,	please:

       o   Read	the tool's documentation

       o   Review the tool's known "BUGS"

       o   Test	the tool on a non-production server

       o   Backup your production server and verify the	backups

DESCRIPTION
       pt-variable-advisor examines "SHOW VARIABLES" for bad values and
       settings	according to the "RULES" described below.  It reports on
       variables that match the	rules, so you can find bad settings in your
       MySQL server.

       At the time of this release, pt-variable-advisor	only examples "SHOW
       VARIABLES", but other input sources are planned like "SHOW STATUS" and
       "SHOW SLAVE STATUS".

RULES
       These are the rules that	pt-variable-advisor will apply to SHOW
       VARIABLES.  Each	rule has three parts: an ID, a severity, and a
       description.

       The rule's ID is	a short, unique	name for the rule.  It usually relates
       to the variable that the	rule examines.	If a variable is examined by
       several rules, then the rules' IDs are numbered like "-1", "-2",	"-N".

       The rule's severity is an indication of how important it	is that	this
       rule matched a query.  We use NOTE, WARN, and CRIT to denote these
       levels.

       The rule's description is a textual, human-readable explanation of what
       it means	when a variable	matches	this rule.  Depending on the verbosity
       of the report you generate, you will see	more of	the text in the
       description.  By	default, you'll	see only the first sentence, which is
       sort of a terse synopsis	of the rule's meaning.	At a higher verbosity,
       you'll see subsequent sentences.

       auto_increment
	   severity: note

	   Are you trying to write to more than	one server in a	dual-master or
	   ring	replication configuration?  This is potentially	very dangerous
	   and in most cases is	a serious mistake.  Most people's reasons for
	   doing this are actually not valid at	all.

       concurrent_insert
	   severity: note

	   Holes (spaces left by deletes) in MyISAM tables might never be
	   reused.

       connect_timeout
	   severity: note

	   A large value of this setting can create a denial of	service
	   vulnerability.

       debug
	   severity: crit

	   Servers built with debugging	capability should not be used in
	   production because of the large performance impact.

       delay_key_write
	   severity: warn

	   MyISAM index	blocks are never flushed until necessary.  If there is
	   a server crash, data	corruption on MyISAM tables can	be much	worse
	   than	usual.

       flush
	   severity: warn

	   This	option might decrease performance greatly.

       flush_time
	   severity: warn

	   This	option might decrease performance greatly.

       have_bdb
	   severity: note

	   The BDB engine is deprecated.  If you aren't	using it, you should
	   disable it with the skip_bdb	option.

       init_connect
	   severity: note

	   The init_connect option is enabled on this server.

       init_file
	   severity: note

	   The init_file option	is enabled on this server.

       init_slave
	   severity: note

	   The init_slave option is enabled on this server.

       innodb_additional_mem_pool_size
	   severity: warn

	   This	variable generally doesn't need	to be larger than 20MB.

       innodb_buffer_pool_size
	   severity: warn

	   The InnoDB buffer pool size is unconfigured.	 In a production
	   environment it should always	be configured explicitly, and the
	   default 10MB	size is	not good.

       innodb_checksums
	   severity: warn

	   InnoDB checksums are	disabled.  Your	data is	not protected from
	   hardware corruption or other	errors!

       innodb_doublewrite
	   severity: warn

	   InnoDB doublewrite is disabled.  Unless you use a filesystem	that
	   protects against partial page writes, your data is not safe!

       innodb_fast_shutdown
	   severity: warn

	   InnoDB's shutdown behavior is not the default.  This	can lead to
	   poor	performance, or	the need to perform crash recovery upon
	   startup.

       innodb_flush_log_at_trx_commit-1
	   severity: warn

	   InnoDB is not configured in strictly	ACID mode.  If there is	a
	   crash, some transactions can	be lost.

       innodb_flush_log_at_trx_commit-2
	   severity: warn

	   Setting innodb_flush_log_at_trx_commit to 0 has no performance
	   benefits over setting it to 2, and more types of data loss are
	   possible.  If you are trying	to change it from 1 for	performance
	   reasons, you	should set it to 2 instead of 0.

       innodb_force_recovery
	   severity: warn

	   InnoDB is in	forced recovery	mode!  This should be used only
	   temporarily when recovering from data corruption or other bugs, not
	   for normal usage.

       innodb_lock_wait_timeout
	   severity: warn

	   This	option has an unusually	long value, which can cause system
	   overload if locks are not being released.

       innodb_log_buffer_size
	   severity: warn

	   The InnoDB log buffer size generally	should not be set larger than
	   16MB.  If you are doing large BLOB operations, InnoDB is not	really
	   a good choice of engines anyway.

       innodb_log_file_size
	   severity: warn

	   The InnoDB log file size is set to its default value, which is not
	   usable on production	systems.

       innodb_max_dirty_pages_pct
	   severity: note

	   The innodb_max_dirty_pages_pct is lower than	the default.  This can
	   cause overly	aggressive flushing and	add load to the	I/O system.

       flush_time
	   severity: warn

	   This	setting	is likely to cause very	bad performance	every
	   flush_time seconds.

       key_buffer_size
	   severity: warn

	   The key buffer size is set to its default value, which is not good
	   for most production systems.	 In a production environment,
	   key_buffer_size should be larger than the default 8MB size.

       large_pages
	   severity: note

	   Large pages are enabled.

       locked_in_memory
	   severity: note

	   The server is locked	in memory with --memlock.

       log_warnings-1
	   severity: note

	   Log_warnings	is disabled, so	unusual	events such as statements
	   unsafe for replication and aborted connections will not be logged
	   to the error	log.

       log_warnings-2
	   severity: note

	   Log_warnings	must be	set greater than 1 to log unusual events such
	   as aborted connections.

       low_priority_updates
	   severity: note

	   The server is running with non-default lock priority	for updates.
	   This	could cause update queries to wait unexpectedly	for read
	   queries.

       max_binlog_size
	   severity: note

	   The max_binlog_size is smaller than the default of 1GB.

       max_connect_errors
	   severity: note

	   max_connect_errors should probably be set as	large as your platform
	   allows.

       max_connections
	   severity: warn

	   If the server ever really has more than a thousand threads running,
	   then	the system is likely to	spend more time	scheduling threads
	   than	really doing useful work.  This	variable's value should	be
	   considered in light of your workload.

       myisam_repair_threads
	   severity: note

	   myisam_repair_threads > 1 enables multi-threaded repair, which is
	   relatively untested and is still listed as beta-quality code	in the
	   official documentation.

       old_passwords
	   severity: warn

	   Old-style passwords are insecure.  They are sent in plain text
	   across the wire.

       optimizer_prune_level
	   severity: warn

	   The optimizer will use an exhaustive	search when planning complex
	   queries, which can cause the	planning process to take a long	time.

       port
	   severity: note

	   The server is listening on a	non-default port.

       query_cache_size-1
	   severity: note

	   The query cache does	not scale to large sizes and can cause
	   unstable performance	when larger than 128MB,	especially on multi-
	   core	machines.

       query_cache_size-2
	   severity: warn

	   The query cache can cause severe performance	problems when it is
	   larger than 256MB, especially on multi-core machines.

       read_buffer_size-1
	   severity: note

	   The read_buffer_size	variable should	generally be left at its
	   default unless an expert determines it is necessary to change it.

       read_buffer_size-2
	   severity: warn

	   The read_buffer_size	variable should	not be larger than 8MB.	 It
	   should generally be left at its default unless an expert determines
	   it is necessary to change it.  Making it larger than	2MB can	hurt
	   performance significantly, and can make the server crash, swap to
	   death, or just become extremely unstable.

       read_rnd_buffer_size-1
	   severity: note

	   The read_rnd_buffer_size variable should generally be left at its
	   default unless an expert determines it is necessary to change it.

       read_rnd_buffer_size-2
	   severity: warn

	   The read_rnd_buffer_size variable should not	be larger than 4M.  It
	   should generally be left at its default unless an expert determines
	   it is necessary to change it.

       relay_log_space_limit
	   severity: warn

	   Setting relay_log_space_limit can cause replicas to stop fetching
	   binary logs from their master immediately. This could increase the
	   risk	that your data will be lost if the master crashes. If the
	   replicas have encountered a limit on	relay log space, then it is
	   possible that the latest transactions exist only on the master and
	   no replica has retrieved them.

       slave_net_timeout
	   severity: warn

	   This	variable is set	too high.  This	is too long to wait before
	   noticing that the connection	to the master has failed and retrying.
	   This	should probably	be set to 60 seconds or	less.  It is also a
	   good	idea to	use pt-heartbeat to ensure that	the connection does
	   not appear to time out when the master is simply idle.

       slave_skip_errors
	   severity: crit

	   You should not set this option.  If replication is having errors,
	   you need to find and	resolve	the cause of that; it is likely	that
	   your	slave's	data is	different from the master.  You	can find out
	   with	pt-table-checksum.

       sort_buffer_size-1
	   severity: note

	   The sort_buffer_size	variable should	generally be left at its
	   default unless an expert determines it is necessary to change it.

       sort_buffer_size-2
	   severity: note

	   The sort_buffer_size	variable should	generally be left at its
	   default unless an expert determines it is necessary to change it.
	   Making it larger than a few MB can hurt performance significantly,
	   and can make	the server crash, swap to death, or just become
	   extremely unstable.

       sql_notes
	   severity: note

	   This	server is configured not to log	Note level warnings to the
	   error log.

       sync_frm
	   severity: warn

	   It is best to set sync_frm so that .frm files are flushed safely to
	   disk	in case	of a server crash.

       tx_isolation-1
	   severity: note

	   This	server's transaction isolation level is	non-default.

       tx_isolation-2
	   severity: warn

	   Most	applications should use	the default REPEATABLE-READ
	   transaction isolation level,	or in a	few cases READ-COMMITTED.

       expire_logs_days
	   severity: warn

	   Binary logs are enabled, but	automatic purging is not enabled.  If
	   you do not purge binary logs, your disk will	fill up.  If you
	   delete binary logs externally to MySQL, you will cause unwanted
	   behaviors.  Always ask MySQL	to purge obsolete logs,	never delete
	   them	externally.

       innodb_file_io_threads
	   severity: note

	   This	option is useless except on Windows.

       innodb_data_file_path
	   severity: note

	   Auto-extending InnoDB files can consume a lot of disk space that is
	   very	difficult to reclaim later.  Some people prefer	to set
	   innodb_file_per_table and allocate a	fixed-size file	for ibdata1.

       innodb_flush_method
	   severity: note

	   Most	production database servers that use InnoDB should set
	   innodb_flush_method to O_DIRECT to avoid double-buffering, unless
	   the I/O system is very low performance.

       innodb_locks_unsafe_for_binlog
	   severity: warn

	   This	option makes point-in-time recovery from binary	logs, and
	   replication,	untrustworthy if statement-based logging is used.

       innodb_support_xa
	   severity: warn

	   MySQL's internal XA transaction support between InnoDB and the
	   binary log is disabled.  The	binary log might not match InnoDB's
	   state after crash recovery, and replication might drift out of sync
	   due to out-of-order statements in the binary	log.

       log_bin
	   severity: warn

	   Binary logging is disabled, so point-in-time	recovery and
	   replication are not possible.

       log_output
	   severity: warn

	   Directing log output	to tables has a	high performance impact.

       max_relay_log_size
	   severity: note

	   A custom max_relay_log_size is defined.

       myisam_recover_options
	   severity: warn

	   myisam_recover_options should be set	to some	value such as
	   BACKUP,FORCE	to ensure that table corruption	is noticed.

       storage_engine
	   severity: note

	   The server is using a non-standard storage engine as	default.

       sync_binlog
	   severity: warn

	   Binary logging is enabled, but sync_binlog isn't configured so that
	   every transaction is	flushed	to the binary log for durability.

       tmp_table_size
	   severity: note

	   The effective minimum size of in-memory implicit temporary tables
	   used	internally during query	execution is min(tmp_table_size,
	   max_heap_table_size), so max_heap_table_size	should be at least as
	   large as tmp_table_size.

       old mysql version
	   severity: warn

	   These are the recommended minimum version for each major release:
	   3.23, 4.1.20, 5.0.37, 5.1.30.

       end-of-life mysql version
	   severity: note

	   Every release older than 5.1	is now officially end-of-life.

OPTIONS
       This tool accepts additional command-line arguments.  Refer to the
       "SYNOPSIS" and usage information	for details.

       --ask-pass
	   Prompt for a	password when connecting to MySQL.

       --charset
	   short form: -A; type: string

	   Default character set.  If the value	is utf8, sets Perl's binmode
	   on STDOUT to	utf8, passes the mysql_enable_utf8 option to
	   DBD::mysql, and runs	SET NAMES UTF8 after connecting	to MySQL.  Any
	   other value sets binmode on STDOUT without the utf8 layer, and runs
	   SET NAMES after connecting to MySQL.

       --config
	   type: Array

	   Read	this comma-separated list of config files; if specified, this
	   must	be the first option on the command line.

       --daemonize
	   Fork	to the background and detach from the shell.  POSIX operating
	   systems only.

       --database
	   short form: -D; type: string

	   Connect to this database.

       --defaults-file
	   short form: -F; type: string

	   Only	read mysql options from	the given file.	 You must give an
	   absolute pathname.

       --help
	   Show	help and exit.

       --host
	   short form: -h; type: string

	   Connect to host.

       --ignore-rules
	   type: hash

	   Ignore these	rule IDs.

	   Specify a comma-separated list of rule IDs (e.g.
	   LIT.001,RES.002,etc.)  to ignore.

       --password
	   short form: -p; type: string

	   Password to use when	connecting.  If	password contains commas they
	   must	be escaped with	a backslash: "exam\,ple"

       --pid
	   type: string

	   Create the given PID	file.  The tool	won't start if the PID file
	   already exists and the PID it contains is different than the
	   current PID.	 However, if the PID file exists and the PID it
	   contains is no longer running, the tool will	overwrite the PID file
	   with	the current PID.  The PID file is removed automatically	when
	   the tool exits.

       --port
	   short form: -P; type: int

	   Port	number to use for connection.

       --set-vars
	   type: Array

	   Set the MySQL variables in this comma-separated list	of
	   "variable=value" pairs.

	   By default, the tool	sets:

	      wait_timeout=10000

	   Variables specified on the command line override these defaults.
	   For example,	specifying "--set-vars wait_timeout=500" overrides the
	   defaultvalue	of 10000.

	   The tool prints a warning and continues if a	variable cannot	be
	   set.

       --socket
	   short form: -S; type: string

	   Socket file to use for connection.

       --source-of-variables
	   type: string; default: mysql

	   Read	"SHOW VARIABLES" from this source.  Possible values are
	   "mysql", "none" or a	file name.  If "mysql" is specified then you
	   must	also specify a DSN on the command line.

       --user
	   short form: -u; type: string

	   User	for login if not current user.

       --verbose
	   short form: -v; cumulative: yes; default: 1

	   Increase verbosity of output.  At the default level of verbosity,
	   the program prints only the first sentence of each rule's
	   description.	 At higher levels, the program prints more of the
	   description.

       --version
	   Show	version	and exit.

       --[no]version-check
	   default: yes

	   Check for the latest	version	of Percona Toolkit, MySQL, and other
	   programs.

	   This	is a standard "check for updates automatically"	feature, with
	   two additional features. First, the tool checks its own version and
	   also	the versions of	the following software:	operating system,
	   Percona Monitoring and Management (PMM), MySQL, Perl, MySQL driver
	   for Perl (DBD::mysql), and Percona Toolkit. Second, it checks for
	   and warns about versions with known problems. For example, MySQL
	   5.5.25 had a	critical bug and was re-released as 5.5.25a.

	   A secure connection to Perconaas Version Check database server is
	   done	to perform these checks. Each request is logged	by the server,
	   including software version numbers and unique ID of the checked
	   system. The ID is generated by the Percona Toolkit installation
	   script or when the Version Check database call is done for the
	   first time.

	   Any updates or known	problems are printed to	STDOUT before the
	   tool's normal output. This feature should never interfere with the
	   normal operation of the tool.

	   For more information, visit
	   <https://www.percona.com/doc/percona-toolkit/LATEST/version-check.html>.

DSN OPTIONS
       These DSN options are used to create a DSN.  Each option	is given like
       "option=value".	The options are	case-sensitive,	so P and p are not the
       same option.  There cannot be whitespace	before or after	the "="	and if
       the value contains whitespace it	must be	quoted.	 DSN options are
       comma-separated.	 See the percona-toolkit manpage for full details.

       o   A

	   dsn:	charset; copy: yes

	   Default character set.

       o   D

	   dsn:	database; copy:	yes

	   Default database.

       o   F

	   dsn:	mysql_read_default_file; copy: yes

	   Only	read default options from the given file

       o   h

	   dsn:	host; copy: yes

	   Connect to host.

       o   p

	   dsn:	password; copy:	yes

	   Password to use when	connecting.  If	password contains commas they
	   must	be escaped with	a backslash: "exam\,ple"

       o   P

	   dsn:	port; copy: yes

	   Port	number to use for connection.

       o   S

	   dsn:	mysql_socket; copy: yes

	   Socket file to use for connection.

       o   u

	   dsn:	user; copy: yes

	   User	for login if not current user.

ENVIRONMENT
       The environment variable	"PTDEBUG" enables verbose debugging output to
       STDERR.	To enable debugging and	capture	all output to a	file, run the
       tool like:

	  PTDEBUG=1 pt-variable-advisor	... > FILE 2>&1

       Be careful: debugging output is voluminous and can generate several
       megabytes of output.

SYSTEM REQUIREMENTS
       You need	Perl, DBI, DBD::mysql, and some	core packages that ought to be
       installed in any	reasonably new version of Perl.

BUGS
       For a list of known bugs, see
       <http://www.percona.com/bugs/pt-variable-advisor>.

       Please report bugs at <https://jira.percona.com/projects/PT>.  Include
       the following information in your bug report:

       o   Complete command-line used to run the tool

       o   Tool	"--version"

       o   MySQL version of all	servers	involved

       o   Output from the tool	including STDERR

       o   Input files (log/dump/config	files, etc.)

       If possible, include debugging output by	running	the tool with
       "PTDEBUG"; see "ENVIRONMENT".

DOWNLOADING
       Visit <http://www.percona.com/software/percona-toolkit/>	to download
       the latest release of Percona Toolkit.  Or, get the latest release from
       the command line:

	  wget percona.com/get/percona-toolkit.tar.gz

	  wget percona.com/get/percona-toolkit.rpm

	  wget percona.com/get/percona-toolkit.deb

       You can also get	individual tools from the latest release:

	  wget percona.com/get/TOOL

       Replace "TOOL" with the name of any tool.

AUTHORS
       Baron Schwartz and Daniel Nichter

ABOUT PERCONA TOOLKIT
       This tool is part of Percona Toolkit, a collection of advanced command-
       line tools for MySQL developed by Percona.  Percona Toolkit was forked
       from two	projects in June, 2011:	Maatkit	and Aspersa.  Those projects
       were created by Baron Schwartz and primarily developed by him and
       Daniel Nichter.	Visit <http://www.percona.com/software/> to learn
       about other free, open-source software from Percona.

COPYRIGHT, LICENSE, AND	WARRANTY
       This program is copyright 2010-2018 Percona LLC and/or its affiliates.

       THIS PROGRAM IS PROVIDED	"AS IS"	AND WITHOUT ANY	EXPRESS	OR IMPLIED
       WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
       MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

       This program is free software; you can redistribute it and/or modify it
       under the terms of the GNU General Public License as published by the
       Free Software Foundation, version 2; OR the Perl	Artistic License.  On
       UNIX and	similar	systems, you can issue `man perlgpl' or	`man
       perlartistic' to	read these licenses.

       You should have received	a copy of the GNU General Public License along
       with this program; if not, write	to the Free Software Foundation, Inc.,
       59 Temple Place,	Suite 330, Boston, MA  02111-1307  USA.

VERSION
       pt-variable-advisor 3.2.0

POD ERRORS
       Hey! The	above document had some	coding errors, which are explained
       below:

       Around line 6095:
	   Non-ASCII character seen before =encoding in	'Perconaas'. Assuming
	   UTF-8

perl v5.32.0			  2020-04-23		PT-VARIABLE-ADVISOR(1)

NAME | SYNOPSIS | RISKS | DESCRIPTION | RULES | OPTIONS | DSN OPTIONS | ENVIRONMENT | SYSTEM REQUIREMENTS | BUGS | DOWNLOADING | AUTHORS | ABOUT PERCONA TOOLKIT | COPYRIGHT, LICENSE, AND WARRANTY | VERSION | POD ERRORS

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