<p>Even though MOT is fully ACID-compliant (as described in the section), not all isolation levels are supported in openGauss 1.0. The following table describes all isolation levels, as well as what is and what is not supported by MOT.</p>
<p><strong>Table 1</strong> Isolation Levels</p>
<div class="hn-table">
<table>
<thead>
<tr>
<td><strong>Isolation Level</strong></td><td><strong>Description</strong></td></tr>
</thead>
<tbody>
<tr>
<td>READ UNCOMMITTED</td><td><strong>Not supported by MOT.</strong></td></tr>
<tr>
<td>READ COMMITTED</td><td><strong>Supported by MOT.</strong></td></tr>
<tr>
<td>SNAPSHOT</td><td><strong>Supported by MOT.</strong></td></tr>
<tr>
<td>REPEATABLE READ</td><td><strong>Supported by MOT.</strong></td></tr>
<tr>
<td>SERIALIZABLE</td><td><strong>Not supported by MOT</strong>.</td></tr>
</tbody>
</table>
</div><p>The following table shows the concurrency side effects enabled by the different isolation levels.</p>
<p><strong>Table 2</strong> Concurrency Side Effects Enabled by Isolation Levels</p>
<div class="hn-table">
<table>
<thead>
<tr>
<td><strong>Isolation Level</strong></td><td><strong>Description</strong></td><td><strong>Non-repeatable Read</strong></td><td><strong>Phantom</strong></td></tr>
</thead>
<tbody>
<tr>
<td>READ UNCOMMITTED</td><td>Yes</td><td>Yes</td><td>Yes</td></tr>
<tr>
<td>READ COMMITTED</td><td>No</td><td>Yes</td><td>Yes</td></tr>
<tr>
<td>REPEATABLE READ</td><td>No</td><td>No</td><td>Yes</td></tr>
<tr>
<td>SNAPSHOT</td><td>No</td><td>No</td><td>No</td></tr>
<tr>
<td>SERIALIZABLE</td><td>No</td><td>No</td><td>No</td></tr>
</tbody>
</table>
</div>

Even though MOT is fully ACID-compliant (as described in the section), not all isolation levels are supported in openGauss 1.0. The following table describes all isolation levels, as well as what is and what is not supported by MOT.

**Table 1** Isolation Levels

| **Isolation Level** | **Description** |
| --- | --- |
| READ UNCOMMITTED | **Not supported by MOT.** |
| READ COMMITTED | **Supported by MOT.** |
| SNAPSHOT | **Supported by MOT.** |
| REPEATABLE READ | **Supported by MOT.** |
| SERIALIZABLE | **Not supported by MOT**. |

The following table shows the concurrency side effects enabled by the different isolation levels.

**Table 2** Concurrency Side Effects Enabled by Isolation Levels

| **Isolation Level** | **Description** | **Non-repeatable Read** | **Phantom** |
| --- | --- | --- | --- |
| READ UNCOMMITTED | Yes | Yes | Yes |
| READ COMMITTED | No | Yes | Yes |
| REPEATABLE READ | No | No | Yes |
| SNAPSHOT | No | No | No |
| SERIALIZABLE | No | No | No |

Isolation Level	Description
READ UNCOMMITTED	Not supported by MOT.
READ COMMITTED	Supported by MOT.
SNAPSHOT	Supported by MOT.
REPEATABLE READ	Supported by MOT.
SERIALIZABLE	Not supported by MOT.

Isolation Level	Description	Non-repeatable Read	Phantom
READ UNCOMMITTED	Yes	Yes	Yes
READ COMMITTED	No	Yes	Yes
REPEATABLE READ	No	No	Yes
SNAPSHOT	No	No	No
SERIALIZABLE	No	No	No

openGauss MOT Isolation Levels