- Microsoft recommends Cached mode for shared mailboxes
- It insulates users from network latency and connectivity issues while they are using Outlook. local cached information is always faster and Outlook prefers to get data from the OST whenever possible
- Why do we recommend cached mode
- Outlook 2013 changes its cached model to allow users to selectively keep a certain amount of data cached in the local OST while the remainder is held in the online mailbox. The theory here is that as we deal with larger and larger mailboxes, it does not make much sense to keep everything cached because users really only need access to their most recent data.
- Most users find that Cached Exchange Mode performs faster than online mode. However, several factors can influence a user’s perception of Cached Exchange Mode performance, like hard disk size and speed, CPU speed, .ost file size, and the expected level of performance.
- By default, when Cached Exchange Mode is enabled in Outlook 2013 and Outlook 2010, shared mail and non-mail folders that users access in other mailboxes, are downloaded and cached in the user’s local .ost file. Cached folders enable offline access and can provide a much more reliable experience on slow or unreliable networks. But be aware that cached folders do take a little more time to populate at first
- What are pros and cons
- By default, when Cached Exchange Mode is enabled in Outlook 2013 and Outlook 2010, shared mail and non-mail folders that users access in other mailboxes, are downloaded and cached in the user’s local .ost file
- For example, if a coworker 1 shares a calendar with coworker 2 and coworker 2 opens it, Outlook 2013 starts caching the folder locally so that coworker 2 has offline access to the folder and is insulated from potential network issues. Similarly, if a manager delegates access to his or her Inbox to a team member, when the team member accesses the folder, Outlook 2013 also starts caching the Inbox folder locally.
- Cached folders enable offline access and can provide a much more reliable experience on slow or unreliable networks
- Portable computer users who frequently move in and out of connectivity.
- Users who frequently work offline or without connectivity.
- By default, when you install Outlook 2013 and enable Cached Exchange Mode, a new compressed version of the Outlook data file (.ost) is created. This new compressed version of the .ost is up to 40% smaller than the size of the .ost files that were created in earlier versions of Outlook.
- In addition, be aware that caching for shared folders works differently from other caching for Cached Exchange Mode. For shared folders, replication to the local .ost file starts only when the user chooses the shared folder. After a user starts caching for the folder by choosing (clicking) it, Outlook updates the folder exactly like other Outlook folders that are synchronized in Cached Exchange Mode. However, if the user does not go to the folder at least one time every 45 days (the default value), the locally cached data for the folder is removed from the .ost file and will not be downloaded until the user chooses on the folder again.
- How to prevent the cons
- If you are moving from using Online Mode to Cached Exchange Mode as part of the deployment of Outlook 2013, be aware that users’ local .ost files can increase 50 percent to 80 percent over the size of the mailbox that is reported in Exchange Server. The format that Outlook uses to store data locally for Cached Exchange Mode is less space-efficient than the server data file format. This means that more disk space is used when mailboxes are downloaded to provide a local copy for Cached Exchange Mode.
- Large mailboxes on computers that don’t have sufficient hard disk space for a local copy of the mailbox.
- Large mailboxes (greater than 25 GB). For large mailboxes, performance can become an issue in Cached Exchange Mode. Choose the slider outlook to reduce the size of OST
- If you plan to upgrade a large group of users from an Online Mode deployment of Outlook to Outlook 2013 with Cached Exchange Mode enabled, stage the rollout over a period of time. A staged rollout helps your organization’s Exchange Server computers manage the requirements of creating or updating users’ .ost files. If most user accounts are updated to use Cached Exchange Mode at the same time and then start Outlook at the same time (for example, on a Monday morning after a weekend upgrade), the Exchange Server computers may have significant performance issues—so a staged approach is preferable.
- If you have a large .pst or .ost file, you may experience application pauses while you perform typical operations in Outlook. These typical operations include reading email messages, moving email messages, and deleting email messages. Up to 5 GB: This file size should provide a good user experience on most hardware.
- The following list summarizes expected behavior based on the size of your Outlook data file.
Between 5 and 10 GB: This file size is typically hardware dependent. Therefore, if you have a fast hard disk and lots of RAM, your experience will be better. However, slower hard disk drives, such as drives that are typically found on portable computers or early-generation solid-state drives (SSDs), experience some application pauses when the drives respond.
More than 10 GB: When the .ost file reaches this size, short pauses begin to occur on most hardware.
very large (25 GB or larger): An .ost file of this size increases the frequency of short pauses, especially while you are downloading new email messages. However, you can use Send/Receive groups to manually sync your mail.
Choose the Mails to keep offline slider in outlook to reduce the size of OST and maintain the value that works optimum in the environment