Using SNAplus2 in a High Availability Environment
Using SNAplus2 with MC/ServiceGuard
| Customizing the SNAplus2 Package Control |
| Script |
| The last step in defining an SNAplus2 package is customizing the |
| Package Control Script to instruct ServiceGuard how to start and stop |
| the SNAplus2 software associated with the package. The example file |
| that we used in our list of suggestions is |
| /etc/cmcluster/sna/sna.cntl. See Table |
| Defining the SNAplus2 Package.” To customize the Package Control |
| Script, you must use an editor like vi. Package Control Script |
| customization cannot be done using SAM. |
| Modifying the PATH variable |
| Since the run and halt commands will use SNAplus2 executable |
| programs, you must add the SNAplus2 executable directory to the PATH |
| variable in the Package Control Script. Add the directory |
| /opt/sna/bin to the PATH variable. |
| Adding Customer Defined Functions |
| To finish the SNAplus2 package definition, add commands to start and |
| stop the SNAplus2 package to the Package Control Script. The |
| commands you will use depend on your specific SNA network |
| configuration. If possible, design the run and halt commands to migrate |
| the SNAplus2 package to another server transparently; that is, without |
| impacting the applications. For the best level of application |
| transparency, we recommend that you use a client/server configuration, |
| and that you configure ServiceGuard to activate the same SNAplus2 |
| node, port, and LS on the backup server that is configured to run on the |
| primary server. This way, the SNAplus2 applications can access the same |
| set of LUs whether the SNA network connectivity is being provided by |
| the primary server or the backup server. |
| We recommend that you use a client/server configuration in high |
NOTE | |
| availability environments. |
| The run and halt commands must be designed to allow ServiceGuard to |
| |
| migrate the SNAplus2 package from the primary server to the backup |
| server. If the SNAplus2 package fails on the primary server (which is |
| indicated by the termination of the snapmon process), ServiceGuard |
| will invoke the halt commands on the primary server. Most often the |
| command, snap stop, is sufficient because that command will halt all of |
376 | Appendix D |