### 28.4.3 sys Schema Views

[28.4.3.1 The host\_summary and x$host\_summary Views](sys-host-summary.html)
[28.4.3.2 The host\_summary\_by\_file\_io and x$host\_summary\_by\_file\_io Views](sys-host-summary-by-file-io.html)
[28.4.3.3 The host\_summary\_by\_file\_io\_type and x$host\_summary\_by\_file\_io\_type Views](sys-host-summary-by-file-io-type.html)
[28.4.3.4 The host\_summary\_by\_stages and x$host\_summary\_by\_stages Views](sys-host-summary-by-stages.html)
[28.4.3.5 The host\_summary\_by\_statement\_latency and x$host\_summary\_by\_statement\_latency Views](sys-host-summary-by-statement-latency.html)
[28.4.3.6 The host\_summary\_by\_statement\_type and x$host\_summary\_by\_statement\_type Views](sys-host-summary-by-statement-type.html)
[28.4.3.7 The innodb\_buffer\_stats\_by\_schema and x$innodb\_buffer\_stats\_by\_schema Views](sys-innodb-buffer-stats-by-schema.html)
[28.4.3.8 The innodb\_buffer\_stats\_by\_table and x$innodb\_buffer\_stats\_by\_table Views](sys-innodb-buffer-stats-by-table.html)
[28.4.3.9 The innodb\_lock\_waits and x$innodb\_lock\_waits Views](sys-innodb-lock-waits.html)
[28.4.3.10 The io\_by\_thread\_by\_latency and x$io\_by\_thread\_by\_latency Views](sys-io-by-thread-by-latency.html)
[28.4.3.11 The io\_global\_by\_file\_by\_bytes and x$io\_global\_by\_file\_by\_bytes Views](sys-io-global-by-file-by-bytes.html)
[28.4.3.12 The io\_global\_by\_file\_by\_latency and x$io\_global\_by\_file\_by\_latency Views](sys-io-global-by-file-by-latency.html)
[28.4.3.13 The io\_global\_by\_wait\_by\_bytes and x$io\_global\_by\_wait\_by\_bytes Views](sys-io-global-by-wait-by-bytes.html)
[28.4.3.14 The io\_global\_by\_wait\_by\_latency and x$io\_global\_by\_wait\_by\_latency Views](sys-io-global-by-wait-by-latency.html)
[28.4.3.15 The latest\_file\_io and x$latest\_file\_io Views](sys-latest-file-io.html)
[28.4.3.16 The memory\_by\_host\_by\_current\_bytes and x$memory\_by\_host\_by\_current\_bytes Views](sys-memory-by-host-by-current-bytes.html)
[28.4.3.17 The memory\_by\_thread\_by\_current\_bytes and x$memory\_by\_thread\_by\_current\_bytes Views](sys-memory-by-thread-by-current-bytes.html)
[28.4.3.18 The memory\_by\_user\_by\_current\_bytes and x$memory\_by\_user\_by\_current\_bytes Views](sys-memory-by-user-by-current-bytes.html)
[28.4.3.19 The memory\_global\_by\_current\_bytes and x$memory\_global\_by\_current\_bytes Views](sys-memory-global-by-current-bytes.html)
[28.4.3.20 The memory\_global\_total and x$memory\_global\_total Views](sys-memory-global-total.html)
[28.4.3.21 The metrics View](sys-metrics.html)
[28.4.3.22 The processlist and x$processlist Views](sys-processlist.html)
[28.4.3.23 The ps\_check\_lost\_instrumentation View](sys-ps-check-lost-instrumentation.html)
[28.4.3.24 The schema\_auto\_increment\_columns View](sys-schema-auto-increment-columns.html)
[28.4.3.25 The schema\_index\_statistics and x$schema\_index\_statistics Views](sys-schema-index-statistics.html)
[28.4.3.26 The schema\_object\_overview View](sys-schema-object-overview.html)
[28.4.3.27 The schema\_redundant\_indexes and x$schema\_flattened\_keys Views](sys-schema-redundant-indexes.html)
[28.4.3.28 The schema\_table\_lock\_waits and x$schema\_table\_lock\_waits Views](sys-schema-table-lock-waits.html)
[28.4.3.29 The schema\_table\_statistics and x$schema\_table\_statistics Views](sys-schema-table-statistics.html)
[28.4.3.30 The schema\_table\_statistics\_with\_buffer and x$schema\_table\_statistics\_with\_buffer Views](sys-schema-table-statistics-with-buffer.html)
[28.4.3.31 The schema\_tables\_with\_full\_table\_scans and x$schema\_tables\_with\_full\_table\_scans Views](sys-schema-tables-with-full-table-scans.html)
[28.4.3.32 The schema\_unused\_indexes View](sys-schema-unused-indexes.html)
[28.4.3.33 The session and x$session Views](sys-session.html)
[28.4.3.34 The session\_ssl\_status View](sys-session-ssl-status.html)
[28.4.3.35 The statement\_analysis and x$statement\_analysis Views](sys-statement-analysis.html)
[28.4.3.36 The statements\_with\_errors\_or\_warnings and x$statements\_with\_errors\_or\_warnings Views](sys-statements-with-errors-or-warnings.html)
[28.4.3.37 The statements\_with\_full\_table\_scans and x$statements\_with\_full\_table\_scans Views](sys-statements-with-full-table-scans.html)
[28.4.3.38 The statements\_with\_runtimes\_in\_95th\_percentile and x$statements\_with\_runtimes\_in\_95th\_percentile Views](sys-statements-with-runtimes-in-95th-percentile.html)
[28.4.3.39 The statements\_with\_sorting and x$statements\_with\_sorting Views](sys-statements-with-sorting.html)
[28.4.3.40 The statements\_with\_temp\_tables and x$statements\_with\_temp\_tables Views](sys-statements-with-temp-tables.html)
[28.4.3.41 The user\_summary and x$user\_summary Views](sys-user-summary.html)
[28.4.3.42 The user\_summary\_by\_file\_io and x$user\_summary\_by\_file\_io Views](sys-user-summary-by-file-io.html)
[28.4.3.43 The user\_summary\_by\_file\_io\_type and x$user\_summary\_by\_file\_io\_type Views](sys-user-summary-by-file-io-type.html)
[28.4.3.44 The user\_summary\_by\_stages and x$user\_summary\_by\_stages Views](sys-user-summary-by-stages.html)
[28.4.3.45 The user\_summary\_by\_statement\_latency and x$user\_summary\_by\_statement\_latency Views](sys-user-summary-by-statement-latency.html)
[28.4.3.46 The user\_summary\_by\_statement\_type and x$user\_summary\_by\_statement\_type Views](sys-user-summary-by-statement-type.html)
[28.4.3.47 The version View](sys-version.html)
[28.4.3.48 The wait\_classes\_global\_by\_avg\_latency and x$wait\_classes\_global\_by\_avg\_latency Views](sys-wait-classes-global-by-avg-latency.html)
[28.4.3.49 The wait\_classes\_global\_by\_latency and x$wait\_classes\_global\_by\_latency
Views](sys-wait-classes-global-by-latency.html)
[28.4.3.50 The waits\_by\_host\_by\_latency and x$waits\_by\_host\_by\_latency Views](sys-waits-by-host-by-latency.html)
[28.4.3.51 The waits\_by\_user\_by\_latency and x$waits\_by\_user\_by\_latency Views](sys-waits-by-user-by-latency.html)
[28.4.3.52 The waits\_global\_by\_latency and x$waits\_global\_by\_latency Views](sys-waits-global-by-latency.html)

 The following sections describe [`sys`](sys-schema.html) schema views.

[]()[]()

 The `sys` schema contains many views that summarize Performance Schema tables in various ways. Most of these views come in pairs, such that one member of the pair has the same name as the other member, plus a `x$` prefix. For example, the [`host_summary_by_file_io`](sys-host-summary-by-file-io.html) view summarizes file I/O grouped by host and displays latencies converted from picoseconds to more readable values (with units);

```
mysql> SELECT * FROM sys.host_summary_by_file_io;
+------------+-------+------------+
| host       | ios   | io_latency |
+------------+-------+------------+
| localhost  | 67570 | 5.38 s     |
| background |  3468 | 4.18 s     |
+------------+-------+------------+
```

 The [`x$host_summary_by_file_io`](sys-host-summary-by-file-io.html) view summarizes the same data but displays unformatted picosecond latencies:

```
mysql> SELECT * FROM sys.x$host_summary_by_file_io;
+------------+-------+---------------+
| host       | ios   | io_latency    |
+------------+-------+---------------+
| localhost  | 67574 | 5380678125144 |
| background |  3474 | 4758696829416 |
+------------+-------+---------------+
```

 The view without the `x$` prefix is intended to provide output that is more user friendly and easier to read. The view with the `x$` prefix that displays the same values in raw form is intended more for use with other tools that perform their own processing on the data.

 Views without the `x$` prefix differ from the corresponding `x$` views in these ways:

* Byte counts are formatted with size units using [`format_bytes()`](sys-format-bytes.html).

* Time values are formatted with temporal units using [`format_time()`](sys-format-time.html).

* SQL statements are truncated to a maximum display width using [`format_statement()`](sys-format-statement.html).

* Path name are shortened using [`format_path()`](sys-format-path.html).

