# setReservedMemSize {#setreservedmemsize}

**Parent topic:**[Functions](../../Functions/category.md)

## Syntax {#syntax}

`setReservedMemSize(memSizeGB)`

## Arguments {#arguments}

**memSizeGB** is a numeric scalar \(in GB\). It is greater than 0 and less than *maxMemSize* \* 0.5.

## Details {#details}

Modify the reserved memory allocated to DolphinDB online. This command can only be executed by the admin.

**Note:**

-   The modified configuration will expire after the cluster is rebooted. To make it permanent, please change the configuration parameter *reservedMemSize*.
-   The total of the reserved memory \(configured via *reservedMemSize*\) and the emergency memory \(configured via *emergencyMemSize*or dynamically adjusted using `setMaxMemSize`\) must not exceed 50% of the current maximum memory limit, which is set via *maxMemSize*or adjusted dynamically using `setMaxMemSize`.

