# PostgreSQL 11

This page describes the Optimization Pack for the component type PostgreSQL 11.

## Metrics

### Concurrency

<table><thead><tr><th width="178">Parameter</th><th width="144.33333333333334">Unit</th><th>Description</th></tr></thead><tbody><tr><td>pg_connections</td><td>connections</td><td>The number of connections in the db.</td></tr></tbody></table>

### Transactions

<table><thead><tr><th width="172">Parameter</th><th width="131.33333333333334">Unit</th><th>Description</th></tr></thead><tbody><tr><td>pg_start_time</td><td>seconds</td><td>The total amount time spent by postresql to boot up.</td></tr><tr><td>pg_commits</td><td>commits/s</td><td>The number of transactions committed per second.</td></tr><tr><td>pg_rollbacks</td><td>rollbacks/s</td><td>The number of transactions rollbacked per second.</td></tr></tbody></table>

### Checkpoints

<table><thead><tr><th width="248.33333333333334">Parameter</th><th width="152">Unit</th><th>Description</th></tr></thead><tbody><tr><td>pg_checkpoint_executed</td><td>checkpoints/s</td><td>The total number of checkpoint operations executed by postgresql.</td></tr></tbody></table>

### Disks

<table><thead><tr><th width="250">Metric</th><th width="131.33333333333334">Unit</th><th>Description</th></tr></thead><tbody><tr><td>pg_disk_used</td><td>bytes</td><td>The amount of disk space used by postgresql.</td></tr><tr><td>pg_blocks_read</td><td>blocks/s</td><td>The number of blocks read per second by postgresql.</td></tr><tr><td>pg_blocks_cache_hit</td><td>blocks/s</td><td>Number of blocks found in the buffer cache.</td></tr><tr><td>pg_backend_fsync_count</td><td>syncs</td><td>The total number of times postgresql executed a sync of data to disk.</td></tr></tbody></table>

## Parameters

### Concurrency

<table><thead><tr><th width="186">Parameter</th><th>Type</th><th width="99">Unit</th><th>Default value</th><th>Domain</th><th>Restart</th><th>Description</th></tr></thead><tbody><tr><td>pg_effective_io_concurrency</td><td>integer</td><td>iops</td><td><code>1</code></td><td><code>0</code> → <code>1000</code></td><td>no</td><td>The number of simultaneous requests that can be handled efficiently by the disk subsystem.</td></tr></tbody></table>

### Background Writer

<table><thead><tr><th width="145">Parameter</th><th width="99">Type</th><th>Unit</th><th>Default value</th><th>Domain</th><th>Restart</th><th>Description</th></tr></thead><tbody><tr><td>pg_bgwriter_delay</td><td>integer</td><td>milliseconds</td><td><code>200</code></td><td><code>10</code> → <code>10000</code></td><td>no</td><td>The delay between activity rounds for the background writer.</td></tr><tr><td>pg_bgwriter_lru_maxpages</td><td>integer</td><td>buffers</td><td><code>100</code></td><td><code>0</code> → <code>1073741823</code></td><td>no</td><td>The maximum number of LRU pages to flush per round by the background writer.</td></tr></tbody></table>

### Checkpoints

| Parameter                          | Type | Unit | Default value | Domain        | Restart | Description                                                                                  |
| ---------------------------------- | ---- | ---- | ------------- | ------------- | ------- | -------------------------------------------------------------------------------------------- |
| pg\_checkpoint\_completion\_target | real |      | `0.5`         | `0.0` → `1.0` | no      | The time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval. |

### Disks

<table><thead><tr><th width="142">Parameter</th><th>Type</th><th width="109">Unit</th><th>Default value</th><th></th><th width="96">Restart</th><th>Description</th></tr></thead><tbody><tr><td>pg_effective_cache_size</td><td>integer</td><td>kilobytes</td><td><code>524288</code></td><td><code>1</code> → <code>2147483647</code></td><td>no</td><td>The planner's assumption about the effective size of the disk cache available to a single query. A higher value makes it more likely index scans will be used, a lower value makes it more likely sequential scans will be used.</td></tr></tbody></table>