By default, the amount of the so-called 'heap' memory available to JIRA Client is limited to 400 MB. If you need to have lots of issues in the local database, you may need to raise this limit. Suppose you'd like to give JIRA Client 512 megabytes at most. Right-click on JIRA Client application and select Show Package Contents. Open Contents folder. Double-click on the Info.plist file. Plist editor should start.

1. Jira Client Download

Jira Client Download

Find the following text and replace 400 with 512 (or any other amount of memory you are ready to give to the client).