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Instructions Instructions

The Advisor system can provide recommendations on server variables by analyzing the server status variables.

Do note however that this system provides recommendations based on simple calculations and by rule of thumb which may not necessarily apply to your system.

Prior to changing any of the configuration, be sure to know what you are changing (by reading the documentation) and how to undo the change. Wrong tuning can have a very negative effect on performance.

The best way to tune your system would be to change only one setting at a time, observe or benchmark your database, and undo the change if there was no clearly measurable improvement.

{"parse":{"errors":[]},"run":{"fired":[{"name":"Long query time","formula":"long_query_time","test":"value >= 10","issue":"{long_query_time} is set to 10 seconds or more, thus only slow queries that take above 10 seconds are logged.","recommendation":"It is suggested to set <a href=\"server_variables.php?filter=long_query_time&amp;lang=en\">long_query_time<\/a> to a lower value, depending on your environment. Usually a value of 1-5 seconds is suggested.","justification":"long_query_time is currently set to 10s.","id":"Long query time"},{"name":"Slow query logging","precondition":"PMA_MYSQL_INT_VERSION >= 50600","formula":"slow_query_log","test":"value == 'OFF'","issue":"The slow query log is disabled.","recommendation":"Enable slow query logging by setting <a href=\"server_variables.php?filter=slow_query_log&amp;lang=en\">slow_query_log<\/a> to 'ON'. This will help troubleshooting badly performing queries.","justification":"slow_query_log is set to 'OFF'","id":"Slow query logging"},{"name":"Query cache disabled","formula":"query_cache_size","test":"value == 0 || query_cache_type == 'OFF' || query_cache_type == '0'","issue":"The query cache is not enabled.","recommendation":"The query cache is known to greatly improve performance if configured correctly. Enable it by setting <a href=\"server_variables.php?filter=query_cache_size&amp;lang=en\">query_cache_size<\/a> to a 2 digit MiB value and setting <a href=\"server_variables.php?filter=query_cache_type&amp;lang=en\">query_cache_type<\/a> to 'ON'. <b>Note:<\/b> If you are using memcached, ignore this recommendation.","justification":"query_cache_size is set to 0 or query_cache_type is set to 'OFF'","id":"Query cache disabled"},{"name":"Sort rows","formula":"Sort_rows \/ Uptime","test":"value * 60 >= 1","issue":"There are lots of rows being sorted.","recommendation":"While there is nothing wrong with a high amount of row sorting, you might want to make sure that the queries which require a lot of sorting use indexed columns in the ORDER BY clause, as this will result in much faster sorting.","justification":"Sorted rows average: 10.76 per minute","id":"Sort rows"},{"name":"Rate of joins without indexes","formula":"(Select_range_check + Select_scan + Select_full_join) \/ Uptime","test":"value * 60 * 60 > 1","issue":"There are too many joins without indexes.","recommendation":"This means that joins are doing full table scans. Adding indexes for the columns being used in the join conditions will greatly speed up table joins.","justification":"Table joins average: 25.95 per minute, this value should be less than 1 per hour","id":"Rate of joins without indexes"},{"name":"Rate of reading first index entry","formula":"Handler_read_first \/ Uptime","test":"value * 60 * 60 > 1","issue":"The rate of reading the first index entry is high.","recommendation":"This usually indicates frequent full index scans. Full index scans are faster than table scans but require lots of CPU cycles in big tables, if those tables that have or had high volumes of UPDATEs and DELETEs, running 'OPTIMIZE TABLE' might reduce the amount of and\/or speed up full index scans. Other than that full index scans can only be reduced by rewriting queries.","justification":"Index scans average: 2.87 per minute, this value should be less than 1 per hour","id":"Rate of reading first index entry"},{"name":"Rate of reading fixed position","formula":"Handler_read_rnd \/ Uptime","test":"value * 60 * 60 > 1","issue":"The rate of reading data from a fixed position is high.","recommendation":"This indicates that many queries need to sort results and\/or do a full table scan, including join queries that do not use indexes. Add indexes where applicable.","justification":"Rate of reading fixed position average: 10.76 per minute, this value should be less than 1 per hour","id":"Rate of reading fixed position"},{"name":"Rate of reading next table row","formula":"Handler_read_rnd_next \/ Uptime","test":"value * 60 * 60 > 1","issue":"The rate of reading the next table row is high.","recommendation":"This indicates that many queries are doing full table scans. Add indexes where applicable.","justification":"Rate of reading next table row: 9.94 per second, this value should be less than 1 per hour","id":"Rate of reading next table row"},{"name":"Temp disk rate","precondition":"!fired('Percentage of temp tables on disk')","formula":"Created_tmp_disk_tables \/ Uptime","test":"value * 60 * 60 > 1","issue":"Many temporary tables are being written to disk instead of being kept in memory.","recommendation":"Increasing <a href=\"server_variables.php?filter=max_heap_table_size&amp;lang=en\">max_heap_table_size<\/a> and <a href=\"server_variables.php?filter=tmp_table_size&amp;lang=en\">tmp_table_size<\/a> might help. However some temporary tables are always being written to disk, independent of the value of these variables. To eliminate these you will have to rewrite your queries to avoid those conditions (Within a temporary table: Presence of a BLOB or TEXT column or presence of a column bigger than 512 bytes) as mentioned in the <a href=\".\/url.php?url=https%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.5%2Fen%2Finternal-temporary-tables.html\" target=\"_blank\" rel=\"noopener noreferrer\">MySQL Documentation<\/a>","justification":"Rate of temporary tables being written to disk: 3.67 per minute, this value should be less than 1 per hour","id":"Temp disk rate"},{"name":"Max % MyISAM key buffer ever used","precondition":"key_buffer_size > 0","formula":"Key_blocks_used * key_cache_block_size \/ key_buffer_size * 100","test":"value < 95","issue":"MyISAM key buffer (index cache) % used is low.","recommendation":"You may need to decrease the size of <a href=\"server_variables.php?filter=key_buffer_size&amp;lang=en\">key_buffer_size<\/a>, re-examine your tables to see if indexes have been removed, or examine queries and expectations about what indexes are being used.","justification":"max % MyISAM key buffer ever used: 0%, this value should be above 95%","id":"Max % MyISAM key buffer ever used"}],"notfired":[{"name":"Uptime below one day","formula":"Uptime","test":"value < 86400","issue":"Uptime is less than 1 day, performance tuning may not be accurate.","recommendation":"To have more accurate averages it is recommended to let the server run for longer than a day before running this analyzer","justification":"The uptime is only 192 days, 22 hours, 32 minutes and 11 seconds","id":"Uptime below one day"},{"name":"Questions below 1,000","formula":"Questions","test":"value < 1000","issue":"Fewer than 1,000 questions have been run against this server. The recommendations may not be accurate.","recommendation":"Let the server run for a longer time until it has executed a greater amount of queries.","justification":"Current amount of Questions: 20779324","id":"Questions below 1,000"},{"name":"Percentage of slow queries","precondition":"Questions > 0","formula":"Slow_queries \/ Questions * 100","test":"value >= 5","issue":"There is a lot of slow queries compared to the overall amount of Queries.","recommendation":"You might want to increase <a href=\"server_variables.php?filter=long_query_time&amp;lang=en\">long_query_time<\/a> or optimize the queries listed in the slow query log","justification":"The slow query rate should be below 5%, your value is 0%.","id":"Percentage of slow queries"},{"name":"Slow query rate","precondition":"Questions > 0","formula":"(Slow_queries \/ Questions * 100) \/ Uptime","test":"value * 60 * 60 > 1","issue":"There is a high percentage of slow queries compared to the server uptime.","recommendation":"You might want to increase <a href=\"server_variables.php?filter=long_query_time&amp;lang=en\">long_query_time<\/a> or optimize the queries listed in the slow query log","justification":"You have a slow query rate of <0.01 per day per hour, you should have less than 1% per hour.","id":"Slow query rate"},{"name":"Release Series","formula":"version","test":"substr(value,0,2) <= '5.' && substr(value,2,1) < 1","issue":"The MySQL server version less than 5.1.","recommendation":"You should upgrade, as MySQL 5.1 has improved performance, and MySQL 5.5 even more so.","justification":"Current version: 5.7.21-log","id":"Release Series"},{"name":"Minor Version","precondition":"! fired('Release Series')","formula":"version","test":"substr(value,0,2) <= '5.' && substr(value,2,1) <= 1 && substr(value,4,2) < 30","issue":"Version less than 5.1.30 (the first GA release of 5.1).","recommendation":"You should upgrade, as recent versions of MySQL 5.1 have improved performance and MySQL 5.5 even more so.","justification":"Current version: 5.7.21-log","id":"Minor Version"},{"name":"Minor Version","precondition":"! fired('Release Series')","formula":"version","test":"substr(value,0,1) == 5 && substr(value,2,1) == 5 && substr(value,4,2) < 8","issue":"Version less than 5.5.8 (the first GA release of 5.5).","recommendation":"You should upgrade, to a stable version of MySQL 5.5.","justification":"Current version: 5.7.21-log","id":"Minor Version"},{"name":"Distribution","formula":"version_comment","test":"preg_match('\/source\/i',value)","issue":"Version is compiled from source, not a MySQL official binary.","recommendation":"If you did not compile from source, you may be using a package modified by a distribution. The MySQL manual only is accurate for official MySQL binaries, not any package distributions (such as RedHat, Debian\/Ubuntu etc).","justification":"'source' found in version_comment","id":"Distribution"},{"name":"Distribution","formula":"version_comment","test":"preg_match('\/percona\/i',value)","issue":"The MySQL manual only is accurate for official MySQL binaries.","recommendation":"Percona documentation is at <a href=\".\/url.php?url=https%3A%2F%2Fwww.percona.com%2Fsoftware%2Fdocumentation%2F\" target=\"_blank\" rel=\"noopener noreferrer\">https:\/\/www.percona.com\/software\/documentation\/<\/a>","justification":"'percona' found in version_comment","id":"Distribution"},{"name":"MySQL Architecture","formula":"system_memory","test":"value > 3072*1024 && !preg_match('\/64\/',version_compile_machine) && !preg_match('\/64\/',version_compile_os)","issue":"MySQL is not compiled as a 64-bit package.","recommendation":"Your memory capacity is above 3 GiB (assuming the Server is on localhost), so MySQL might not be able to access all of your memory. You might want to consider installing the 64-bit version of MySQL.","justification":"Available memory on this host: 15.51 GiB","id":"MySQL Architecture"},{"name":"Percentage of sorts that cause temporary tables","precondition":"Sort_scan + Sort_range > 0","formula":"Sort_merge_passes \/ (Sort_scan + Sort_range) * 100","test":"value > 10","issue":"Too many sorts are causing temporary tables.","recommendation":"Consider increasing <a href=\"server_variables.php?filter=sort_buffer_size&amp;lang=en\">sort_buffer_size<\/a> and\/or <a href=\"server_variables.php?filter=read_rnd_buffer_size&amp;lang=en\">read_rnd_buffer_size<\/a>, depending on your system memory limits.","justification":"0% of all sorts cause temporary tables, this value should be lower than 10%.","id":"Percentage of sorts that cause temporary tables"},{"name":"Rate of sorts that cause temporary tables","formula":"Sort_merge_passes \/ Uptime","test":"value * 60 * 60 > 1","issue":"Too many sorts are causing temporary tables.","recommendation":"Consider increasing <a href=\"server_variables.php?filter=sort_buffer_size&amp;lang=en\">sort_buffer_size<\/a> and\/or <a href=\"server_variables.php?filter=read_rnd_buffer_size&amp;lang=en\">read_rnd_buffer_size<\/a>, depending on your system memory limits.","justification":"Temporary tables average: <0.01 per day, this value should be less than 1 per hour.","id":"Rate of sorts that cause temporary tables"},{"name":"Different tmp_table_size and max_heap_table_size","formula":"tmp_table_size - max_heap_table_size","test":"value !=0","issue":"{tmp_table_size} and {max_heap_table_size} are not the same.","recommendation":"If you have deliberately changed one of either: The server uses the lower value of either to determine the maximum size of in-memory tables. So if you wish to increase the in-memory table limit you will have to increase the other value as well.","justification":"Current values are tmp_table_size: 16 MiB, max_heap_table_size: 16 MiB","id":"Different tmp_table_size and max_heap_table_size"},{"name":"Percentage of temp tables on disk","precondition":"Created_tmp_tables + Created_tmp_disk_tables > 0","formula":"Created_tmp_disk_tables \/ (Created_tmp_tables + Created_tmp_disk_tables) * 100","test":"value > 25","issue":"Many temporary tables are being written to disk instead of being kept in memory.","recommendation":"Increasing <a href=\"server_variables.php?filter=max_heap_table_size&amp;lang=en\">max_heap_table_size<\/a> and <a href=\"server_variables.php?filter=tmp_table_size&amp;lang=en\">tmp_table_size<\/a> might help. However some temporary tables are always being written to disk, independent of the value of these variables. To eliminate these you will have to rewrite your queries to avoid those conditions (Within a temporary table: Presence of a BLOB or TEXT column or presence of a column bigger than 512 bytes) as mentioned in the beginning of an <a href=\".\/url.php?url=https%3A%2F%2Fwww.facebook.com%2Fnote.php%3Fnote_id%3D10150111255065841%26comments\" target=\"_blank\" rel=\"noopener noreferrer\">Article by the Pythian Group<\/a>","justification":"9% of all temporary tables are being written to disk, this value should be below 25%","id":"Percentage of temp tables on disk"},{"name":"MyISAM key buffer size","formula":"key_buffer_size","test":"value == 0","issue":"Key buffer is not initialized. No MyISAM indexes will be cached.","recommendation":"Set <a href=\"server_variables.php?filter=key_buffer_size&amp;lang=en\">key_buffer_size<\/a> depending on the size of your MyISAM indexes. 64M is a good start.","justification":"key_buffer_size is 0","id":"MyISAM key buffer size"},{"name":"Percentage of index reads from memory","precondition":"Key_read_requests > 0","formula":"100 - (Key_reads \/ Key_read_requests * 100)","test":"value < 95","issue":"The % of indexes that use the MyISAM key buffer is low.","recommendation":"You may need to increase <a href=\"server_variables.php?filter=key_buffer_size&amp;lang=en\">key_buffer_size<\/a>.","justification":"Index reads from memory: 100%, this value should be above 95%","id":"Percentage of index reads from memory"},{"name":"Rate of table open","formula":"Opened_tables \/ Uptime","test":"value*60*60 > 10","issue":"The rate of opening tables is high.","recommendation":"Opening tables requires disk I\/O which is costly. Increasing <a href=\"server_variables.php?filter=table_open_cache&amp;lang=en\">table_open_cache<\/a> might avoid this.","justification":"Opened table rate: 13.52 per day, this value should be less than 10 per hour","id":"Rate of table open"},{"name":"Percentage of used open files limit","formula":"Open_files \/ open_files_limit * 100","test":"value > 85","issue":"The number of open files is approaching the max number of open files. You may get a \"Too many open files\" error.","recommendation":"Consider increasing <a href=\"server_variables.php?filter=open_files_limit&amp;lang=en\">open_files_limit<\/a>, and check the error log when restarting after changing <a href=\"server_variables.php?filter=open_files_limit&amp;lang=en\">open_files_limit<\/a>.","justification":"The number of opened files is at 0% of the limit. It should be below 85%","id":"Percentage of used open files limit"},{"name":"Rate of open files","formula":"Open_files \/ Uptime","test":"value * 60 * 60 > 5","issue":"The rate of opening files is high.","recommendation":"Consider increasing <a href=\"server_variables.php?filter=open_files_limit&amp;lang=en\">open_files_limit<\/a>, and check the error log when restarting after changing <a href=\"server_variables.php?filter=open_files_limit&amp;lang=en\">open_files_limit<\/a>.","justification":"Opened files rate: 0.12 per day, this value should be less than 5 per hour","id":"Rate of open files"},{"name":"Immediate table locks %","precondition":"Table_locks_waited + Table_locks_immediate > 0","formula":"Table_locks_immediate \/ (Table_locks_waited + Table_locks_immediate) * 100","test":"value < 95","issue":"Too many table locks were not granted immediately.","recommendation":"Optimize queries and\/or use InnoDB to reduce lock wait.","justification":"Immediate table locks: 100%, this value should be above 95%","id":"Immediate table locks %"},{"name":"Table lock wait rate","formula":"Table_locks_waited \/ Uptime","test":"value * 60 * 60 > 1","issue":"Too many table locks were not granted immediately.","recommendation":"Optimize queries and\/or use InnoDB to reduce lock wait.","justification":"Table lock wait rate: <0.01 per day, this value should be less than 1 per hour","id":"Table lock wait rate"},{"name":"Thread cache","formula":"thread_cache_size","test":"value < 1","issue":"Thread cache is disabled, resulting in more overhead from new connections to MySQL.","recommendation":"Enable the thread cache by setting <a href=\"server_variables.php?filter=thread_cache_size&amp;lang=en\">thread_cache_size<\/a> > 0.","justification":"The thread cache is set to 0","id":"Thread cache"},{"name":"Thread cache hit rate %","precondition":"thread_cache_size > 0","formula":"100 - Threads_created \/ Connections","test":"value < 80","issue":"Thread cache is not efficient.","recommendation":"Increase <a href=\"server_variables.php?filter=thread_cache_size&amp;lang=en\">thread_cache_size<\/a>.","justification":"Thread cache hitrate: 100%, this value should be above 80%","id":"Thread cache hit rate %"},{"name":"Threads that are slow to launch","precondition":"slow_launch_time > 0","formula":"Slow_launch_threads","test":"value > 0","issue":"There are too many threads that are slow to launch.","recommendation":"This generally happens in case of general system overload as it is pretty simple operations. You might want to monitor your system load carefully.","justification":"0 thread(s) took longer than 2 seconds to start, it should be 0","id":"Threads that are slow to launch"},{"name":"Slow launch time","formula":"slow_launch_time","test":"value > 2","issue":"Slow_launch_time is above 2s.","recommendation":"Set <a href=\"server_variables.php?filter=slow_launch_time&amp;lang=en\">slow_launch_time<\/a> to 1s or 2s to correctly count threads that are slow to launch.","justification":"slow_launch_time is set to 2","id":"Slow launch time"},{"name":"Percentage of used connections","formula":"Max_used_connections \/ max_connections * 100","test":"value > 80","issue":"The maximum amount of used connections is getting close to the value of {max_connections}.","recommendation":"Increase <a href=\"server_variables.php?filter=max_connections&amp;lang=en\">max_connections<\/a>, or decrease <a href=\"server_variables.php?filter=wait_timeout&amp;lang=en\">wait_timeout<\/a> so that connections that do not close database handlers properly get killed sooner. Make sure the code closes database handlers properly.","justification":"Max_used_connections is at 24% of max_connections, it should be below 80%","id":"Percentage of used connections"},{"name":"Percentage of aborted connections","formula":"Aborted_connects \/ Connections * 100","test":"value > 1","issue":"Too many connections are aborted.","recommendation":"Connections are usually aborted when they cannot be authorized. <a href=\".\/url.php?url=https%3A%2F%2Fwww.percona.com%2Fblog%2F2008%2F08%2F23%2Fhow-to-track-down-the-source-of-aborted_connects%2F\" target=\"_blank\" rel=\"noopener noreferrer\">This article<\/a> might help you track down the source.","justification":"0% of all connections are aborted. This value should be below 1%","id":"Percentage of aborted connections"},{"name":"Rate of aborted connections","formula":"Aborted_connects \/ Uptime","test":"value * 60 * 60 > 1","issue":"Too many connections are aborted.","recommendation":"Connections are usually aborted when they cannot be authorized. <a href=\".\/url.php?url=https%3A%2F%2Fwww.percona.com%2Fblog%2F2008%2F08%2F23%2Fhow-to-track-down-the-source-of-aborted_connects%2F\" target=\"_blank\" rel=\"noopener noreferrer\">This article<\/a> might help you track down the source.","justification":"Aborted connections rate is at <0.01 per day, this value should be less than 1 per hour","id":"Rate of aborted connections"},{"name":"Percentage of aborted clients","formula":"Aborted_clients \/ Connections * 100","test":"value > 2","issue":"Too many clients are aborted.","recommendation":"Clients are usually aborted when they did not close their connection to MySQL properly. This can be due to network issues or code not closing a database handler properly. Check your network and code.","justification":"0% of all clients are aborted. This value should be below 2%","id":"Percentage of aborted clients"},{"name":"Rate of aborted clients","formula":"Aborted_clients \/ Uptime","test":"value * 60 * 60 > 1","issue":"Too many clients are aborted.","recommendation":"Clients are usually aborted when they did not close their connection to MySQL properly. This can be due to network issues or code not closing a database handler properly. Check your network and code.","justification":"Aborted client rate is at 0.02 per day, this value should be less than 1 per hour","id":"Rate of aborted clients"},{"name":"InnoDB log size","precondition":"innodb_buffer_pool_size > 0","formula":"innodb_log_file_size \/ innodb_buffer_pool_size * 100","test":"value < 20 && innodb_log_file_size \/ (1024 * 1024) < 256","issue":"The InnoDB log file size is not an appropriate size, in relation to the InnoDB buffer pool.","recommendation":"Especially on a system with a lot of writes to InnoDB tables you should set <a href=\"server_variables.php?filter=innodb_log_file_size&amp;lang=en\">innodb_log_file_size<\/a> to 25% of <a href=\"server_variables.php?filter=innodb_buffer_pool_size&amp;lang=en\">innodb_buffer_pool_size<\/a>. However the bigger this value, the longer the recovery time will be when database crashes, so this value should not be set much higher than 256 MiB. Please note however that you cannot simply change the value of this variable. You need to shutdown the server, remove the InnoDB log files, set the new value in my.cnf, start the server, then check the error logs if everything went fine. See also <a href=\".\/url.php?url=https%3A%2F%2Fmysqldatabaseadministration.blogspot.com%2F2007%2F01%2Fincrease-innodblogfilesize-proper-way.html\" target=\"_blank\" rel=\"noopener noreferrer\">this blog entry<\/a>","justification":"Your InnoDB log size is at 200% in relation to the InnoDB buffer pool size, it should not be below 20%","id":"InnoDB log size"},{"name":"InnoDB buffer pool size","precondition":"system_memory > 0","formula":"innodb_buffer_pool_size \/ system_memory * 100","test":"value < 60","issue":"Your InnoDB buffer pool is fairly small.","recommendation":"The InnoDB buffer pool has a profound impact on performance for InnoDB tables. Assign all your remaining memory to this buffer. For database servers that use solely InnoDB as storage engine and have no other services (e.g. a web server) running, you may set this as high as 80% of your available memory. If that is not the case, you need to carefully assess the memory consumption of your other services and non-InnoDB-Tables and set this variable accordingly. If it is set too high, your system will start swapping, which decreases performance significantly. See also <a href=\".\/url.php?url=https%3A%2F%2Fwww.percona.com%2Fblog%2F2007%2F11%2F03%2Fchoosing-innodb_buffer_pool_size%2F\" target=\"_blank\" rel=\"noopener noreferrer\">this article<\/a>","justification":"You are currently using 412.53660394562% of your memory for the InnoDB buffer pool. This rule fires if you are assigning less than 60%, however this might be perfectly adequate for your system if you don't have much InnoDB tables or other services running on the same machine.","id":"InnoDB buffer pool size"},{"name":"MyISAM concurrent inserts","formula":"concurrent_insert","test":"value === 0 || value === 'NEVER'","issue":"Enable {concurrent_insert} by setting it to 1","recommendation":"Setting <a href=\"server_variables.php?filter=concurrent_insert&amp;lang=en\">concurrent_insert<\/a> to 1 reduces contention between readers and writers for a given table. See also <a href=\".\/url.php?url=https%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.5%2Fen%2Fconcurrent-inserts.html\" target=\"_blank\" rel=\"noopener noreferrer\">MySQL Documentation<\/a>","justification":"concurrent_insert is set to 0","id":"MyISAM concurrent inserts"}],"unchecked":[{"name":"Slow query logging","precondition":"PMA_MYSQL_INT_VERSION < 50600","formula":"log_slow_queries","test":"value == 'OFF'","issue":"The slow query log is disabled.","recommendation":"Enable slow query logging by setting {log_slow_queries} to 'ON'. This will help troubleshooting badly performing queries.","justification":"log_slow_queries is set to 'OFF'"},{"name":"Query caching method","precondition":"!fired('Query cache disabled')","formula":"Questions \/ Uptime","test":"value > 100","issue":"Suboptimal caching method.","recommendation":"You are using the MySQL Query cache with a fairly high traffic database. It might be worth considering to use <a href=\"https:\/\/dev.mysql.com\/doc\/refman\/5.5\/en\/ha-memcached.html\">memcached<\/a> instead of the MySQL Query cache, especially if you have multiple slaves.","justification":"The query cache is enabled and the server receives %d queries per second. This rule fires if there is more than 100 queries per second. | round(value,1)"},{"name":"Query cache efficiency (%)","precondition":"Com_select + Qcache_hits > 0 && !fired('Query cache disabled')","formula":"Qcache_hits \/ (Com_select + Qcache_hits) * 100","test":"value < 20","issue":"Query cache not running efficiently, it has a low hit rate.","recommendation":"Consider increasing {query_cache_limit}.","justification":"The current query cache hit rate of %s% is below 20% | round(value,1)"},{"name":"Query Cache usage","precondition":"!fired('Query cache disabled')","formula":"100 - Qcache_free_memory \/ query_cache_size * 100","test":"value < 80","issue":"Less than 80% of the query cache is being utilized.","recommendation":"This might be caused by {query_cache_limit} being too low. Flushing the query cache might help as well.","justification":"The current ratio of free query cache memory to total query cache size is %s%. It should be above 80% | round(value,1)"},{"name":"Query cache fragmentation","precondition":"!fired('Query cache disabled')","formula":"Qcache_free_blocks \/ (Qcache_total_blocks \/ 2) * 100","test":"value > 20","issue":"The query cache is considerably fragmented.","recommendation":"Severe fragmentation is likely to (further) increase Qcache_lowmem_prunes. This might be caused by many Query cache low memory prunes due to {query_cache_size} being too small. For a immediate but short lived fix you can flush the query cache (might lock the query cache for a long time). Carefully adjusting {query_cache_min_res_unit} to a lower value might help too, e.g. you can set it to the average size of your queries in the cache using this formula: (query_cache_size - qcache_free_memory) \/ qcache_queries_in_cache","justification":"The cache is currently fragmented by %s% , with 100% fragmentation meaning that the query cache is an alternating pattern of free and used blocks. This value should be below 20%. | round(value,1)"},{"name":"Query cache low memory prunes","precondition":"Qcache_inserts > 0 && !fired('Query cache disabled')","formula":"Qcache_lowmem_prunes \/ Qcache_inserts * 100","test":"value > 0.1","issue":"Cached queries are removed due to low query cache memory from the query cache.","recommendation":"You might want to increase {query_cache_size}, however keep in mind that the overhead of maintaining the cache is likely to increase with its size, so do this in small increments and monitor the results.","justification":"The ratio of removed queries to inserted queries is %s%. The lower this value is, the better (This rules firing limit: 0.1%) | round(value,1)"},{"name":"Query cache max size","precondition":"!fired('Query cache disabled')","formula":"query_cache_size","test":"value > 1024 * 1024 * 128","issue":"The query cache size is above 128 MiB. Big query caches may cause significant overhead that is required to maintain the cache.","recommendation":"Depending on your environment, it might be performance increasing to reduce this value.","justification":"Current query cache size: %s | ADVISOR_formatByteDown(value, 2, 2)"},{"name":"Query cache min result size","precondition":"!fired('Query cache disabled')","formula":"query_cache_limit","test":"value == 1024*1024","issue":"The max size of the result set in the query cache is the default of 1 MiB.","recommendation":"Changing {query_cache_limit} (usually by increasing) may increase efficiency. This variable determines the maximum size a query result may have to be inserted into the query cache. If there are many query results above 1 MiB that are well cacheable (many reads, little writes) then increasing {query_cache_limit} will increase efficiency. Whereas in the case of many query results being above 1 MiB that are not very well cacheable (often invalidated due to table updates) increasing {query_cache_limit} might reduce efficiency.","justification":"query_cache_limit is set to 1 MiB"},{"name":"Percentage of MyISAM key buffer used","precondition":"key_buffer_size > 0 && !fired('Max % MyISAM key buffer ever used')","formula":"( 1 - Key_blocks_unused * key_cache_block_size \/ key_buffer_size) * 100","test":"value < 95","issue":"MyISAM key buffer (index cache) % used is low.","recommendation":"You may need to decrease the size of {key_buffer_size}, re-examine your tables to see if indexes have been removed, or examine queries and expectations about what indexes are being used.","justification":"% MyISAM key buffer used: %s%, this value should be above 95% | round(value,1)"},{"name":"Is InnoDB disabled?","precondition":"PMA_MYSQL_INT_VERSION < 50600","formula":"have_innodb","test":"value != \"YES\"","issue":"You do not have InnoDB enabled.","recommendation":"InnoDB is usually the better choice for table engines.","justification":"have_innodb is set to 'value'"},{"name":"Max InnoDB log size","precondition":"innodb_buffer_pool_size > 0 && innodb_log_file_size \/ innodb_buffer_pool_size * 100 < 30","formula":"innodb_log_file_size \/ (1024 * 1024)","test":"value > 256","issue":"The InnoDB log file size is inadequately large.","recommendation":"It is usually sufficient to set {innodb_log_file_size} to 25% of the size of {innodb_buffer_pool_size}. A very big {innodb_log_file_size} slows down the recovery time after a database crash considerably. See also <a href=\"https:\/\/www.percona.com\/blog\/2006\/07\/03\/choosing-proper-innodb_log_file_size\/\">this Article<\/a>. You need to shutdown the server, remove the InnoDB log files, set the new value in my.cnf, start the server, then check the error logs if everything went fine. See also <a href=\"https:\/\/mysqldatabaseadministration.blogspot.com\/2007\/01\/increase-innodblogfilesize-proper-way.html\">this blog entry<\/a>","justification":"Your absolute InnoDB log size is %s MiB | round(value,1)"}],"errors":[]}}
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