> # Guidelines and Limitations

> All switches in the fabric must be CFS capable. A Cisco MDS 9000 Family switch is CFS capable if it is running Cisco SAN-OS Release 2.0(1b) or later, or MDS NX-OS Release 4.1(1) or later. Switches that are not CFS capable do not receive distributions and result in part of the fabric not receiving the intended distribution.

> CFS has the following guidelines and limitations:

> - Implicit CFS usage—The first time you issue a CFS task for a CFS-enabled application, the configuration modification process begins and the application locks the fabric.
> - Pending database—The pending database is a temporary buffer to hold uncommitted information. The uncommitted changes are not applied immediately to ensure that the database is synchronized with the database in the other switches in the fabric. When you commit the changes, the pending database overwrites the configuration database (also known as the active database or the effective database).
> - CFS distribution enabled or disabled on a per-application basis—The default (enable or disable) for CFS distribution state differs between applications. If CFS distribution is disabled for an application, then that application does not distribute any configuration nor does it accept a distribution from other switches in the fabric.
> - Explicit CFS commit—Most applications require an explicit commit operation to copy the changes in the temporary buffer to the application database, to distribute the new database to the fabric, and to release the fabric lock. The changes in the temporary buffer are not applied if you do not perform the commit operation.

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