MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
The Performance Schema implements several status variables that provide information about instrumentation that could not be loaded or created due to memory constraints:
mysql> SHOW STATUS LIKE 'perf%';
+-------------------------------------------------------+-------+
| Variable_name | Value |
+-------------------------------------------------------+-------+
| Performance_schema_accounts_lost | 0 |
| Performance_schema_cond_classes_lost | 0 |
| Performance_schema_cond_instances_lost | 0 |
| Performance_schema_digest_lost | 0 |
| Performance_schema_file_classes_lost | 0 |
| Performance_schema_file_handles_lost | 0 |
| Performance_schema_file_instances_lost | 0 |
| Performance_schema_hosts_lost | 0 |
| Performance_schema_index_stat_lost | 0 |
| Performance_schema_locker_lost | 0 |
| Performance_schema_memory_classes_lost | 0 |
| Performance_schema_metadata_lock_lost | 0 |
| Performance_schema_meter_lost | 0 |
| Performance_schema_metric_lost | 0 |
| Performance_schema_mutex_classes_lost | 0 |
| Performance_schema_mutex_instances_lost | 0 |
| Performance_schema_nested_statement_lost | 0 |
| Performance_schema_prepared_statements_lost | 0 |
| Performance_schema_program_lost | 0 |
| Performance_schema_rwlock_classes_lost | 0 |
| Performance_schema_rwlock_instances_lost | 0 |
| Performance_schema_session_connect_attrs_longest_seen | 131 |
| Performance_schema_session_connect_attrs_lost | 0 |
| Performance_schema_socket_classes_lost | 0 |
| Performance_schema_socket_instances_lost | 0 |
| Performance_schema_stage_classes_lost | 0 |
| Performance_schema_statement_classes_lost | 0 |
| Performance_schema_table_handles_lost | 0 |
| Performance_schema_table_instances_lost | 0 |
| Performance_schema_table_lock_stat_lost | 0 |
| Performance_schema_thread_classes_lost | 0 |
| Performance_schema_thread_instances_lost | 0 |
| Performance_schema_users_lost | 0 |
+-------------------------------------------------------+-------+
For information on using these variables to check Performance Schema status, see Section 29.7, “Performance Schema Status Monitoring”.
Performance Schema status variables have the following meanings:
Performance_schema_accounts_lost
The number of times a row could not be added to the
accounts table because it was
full.
Performance_schema_cond_classes_lost
How many condition instruments could not be loaded.
Performance_schema_cond_instances_lost
How many condition instrument instances could not be created.
Performance_schema_digest_lost
The number of digest instances that could not be instrumented
in the
events_statements_summary_by_digest
table. This can be nonzero if the value of
performance_schema_digests_size
is too small.
Performance_schema_file_classes_lost
How many file instruments could not be loaded.
Performance_schema_file_handles_lost
How many file instrument instances could not be opened.
Performance_schema_file_instances_lost
How many file instrument instances could not be created.
The number of times a row could not be added to the
hosts table because it was full.
Performance_schema_index_stat_lost
The number of indexes for which statistics were lost. This can
be nonzero if the value of
performance_schema_max_index_stat
is too small.
Performance_schema_locker_lost
How many events are “lost” or not recorded, due to the following conditions:
Events are recursive (for example, waiting for A caused a wait on B, which caused a wait on C).
The depth of the nested events stack is greater than the limit imposed by the implementation.
Events recorded by the Performance Schema are not recursive, so this variable should always be 0.
Performance_schema_memory_classes_lost
The number of times a memory instrument could not be loaded.
Performance_schema_metadata_lock_lost
The number of metadata locks that could not be instrumented in
the metadata_locks table. This
can be nonzero if the value of
performance_schema_max_metadata_locks
is too small.
Number of meter instruments that failed to be created.
Performance_schema_metric_lost
Number of metric instruments that failed to be created.
Performance_schema_mutex_classes_lost
How many mutex instruments could not be loaded.
Performance_schema_mutex_instances_lost
How many mutex instrument instances could not be created.
Performance_schema_nested_statement_lost
The number of stored program statements for which statistics
were lost. This can be nonzero if the value of
performance_schema_max_statement_stack
is too small.
Performance_schema_prepared_statements_lost
The number of prepared statements that could not be
instrumented in the
prepared_statements_instances
table. This can be nonzero if the value of
performance_schema_max_prepared_statements_instances
is too small.
Performance_schema_program_lost
The number of stored programs for which statistics were lost.
This can be nonzero if the value of
performance_schema_max_program_instances
is too small.
Performance_schema_rwlock_classes_lost
How many rwlock instruments could not be loaded.
Performance_schema_rwlock_instances_lost
How many rwlock instrument instances could not be created.
Performance_schema_session_connect_attrs_longest_seen
In addition to the connection attribute size-limit check
performed by the Performance Schema against the value of the
performance_schema_session_connect_attrs_size
system variable, the server performs a preliminary check,
imposing a limit of 64KB on the aggregate size of connection
attribute data it accepts. If a client attempts to send more
than 64KB of attribute data, the server rejects the
connection. Otherwise, the server considers the attribute
buffer valid and tracks the size of the longest such buffer in
the
Performance_schema_session_connect_attrs_longest_seen
status variable. If this value is larger than
performance_schema_session_connect_attrs_size,
DBAs may wish to increase the latter value, or, alternatively,
investigate which clients are sending large amounts of
attribute data.
For more information about connection attributes, see Section 29.12.9, “Performance Schema Connection Attribute Tables”.
Performance_schema_session_connect_attrs_lost
The number of connections for which connection attribute
truncation has occurred. For a given connection, if the client
sends connection attribute key-value pairs for which the
aggregate size is larger than the reserved storage permitted
by the value of the
performance_schema_session_connect_attrs_size
system variable, the Performance Schema truncates the
attribute data and increments
Performance_schema_session_connect_attrs_lost.
If this value is nonzero, you may wish to set
performance_schema_session_connect_attrs_size
to a larger value.
For more information about connection attributes, see Section 29.12.9, “Performance Schema Connection Attribute Tables”.
Performance_schema_socket_classes_lost
How many socket instruments could not be loaded.
Performance_schema_socket_instances_lost
How many socket instrument instances could not be created.
Performance_schema_stage_classes_lost
How many stage instruments could not be loaded.
Performance_schema_statement_classes_lost
How many statement instruments could not be loaded.
Performance_schema_table_handles_lost
How many table instrument instances could not be opened. This
can be nonzero if the value of
performance_schema_max_table_handles
is too small.
Performance_schema_table_instances_lost
How many table instrument instances could not be created.
Performance_schema_table_lock_stat_lost
The number of tables for which lock statistics were lost. This
can be nonzero if the value of
performance_schema_max_table_lock_stat
is too small.
Performance_schema_thread_classes_lost
How many thread instruments could not be loaded.
Performance_schema_thread_instances_lost
The number of thread instances that could not be instrumented
in the threads table. This can be
nonzero if the value of
performance_schema_max_thread_instances
is too small.
The number of times a row could not be added to the
users table because it was full.
Performance_schema_logger_lost
Displays the number of logger instruments which failed to be created.