Adding Coservers

You can easily add coservers to expand the database server capacity, either for permanent tables or for special processing needs, without reinitializing the database server. You can add coservers to an Extended Parallel Server system that contains at least one coserver.

To add coservers to expand initial database server capacity

Shut down the database server in two steps:
1. Bring the database server to quiescent mode.
```
xctl onmode -sy
```
2. Shut down the database server completely.
```
xctl onmode -ky
```
Edit the ONCONFIG file to add a new coserver definition section.
- To add a fully capable coserver:
```
COSERVER     n
NODE         node_name
...
END
```
- To add a coserver that adds temporary dbspaces:
```
COSERVER     n
NODE         node_name
CAPABILITIES TEMPDATA
...
END
```
- To add a coserver that increases the number of CPUs:
```
COSERVER     n
NODE         node_name
CAPABILITIES COMPUTE
...
END
```
Tip:

You can define specific-purpose coservers with both TEMPDATA and COMPUTE capabilities. For an example, see Figure 9.
If necessary, edit the new coserver definitions to override global parameter settings for specific coservers.
See Customizing the Coserver Definition.
If you want the new fully capable coservers to allow client connections, edit the sqlhosts file and specify client/server connection information for the new coservers.
(Do not add specific-purpose coservers to the sqlhosts file.) For more information, refer to the IBM Informix: Administrator's Guide.
Restart the database server in two steps:
1. Restart the previously existing coservers and initialize only shared memory.
  For example, if you started with two coservers, enter:
```
xctl -c 1-2 -C oninit -sy
```
2. Start the new coservers and initialize both shared memory and disk space.
  For example, if you added coservers 3 through 5, enter:
```
xctl -c 3-5 -C oninit -iy
```
  If this step fails and a coserver cannot be added, you must delete it manually as described in Removing Specific-Purpose Coservers, redefine the coserver, and add it again.
Add fully capable coservers to the options specified in the BAR_SM section for the storage manager in the ONCONFIG file so that they are backed up appropriately.
Add dbspaces to all new coservers.
For information, see Creating Storage Spaces for Coservers.
Perform level-0 backups of all dbspaces.