If you follow up some Informix related blogs and sites you probably already noticed that the latest IDS 11.50xC2 includes some surprises. Both Guy Bowerman and Eric Herbert mentioned it on their webpages.
I'd like to add a few more comments to their posts. I chose to do this, specially because the release notes don't emphasize enough all the changes. If you're on Windows, please refer to Guy's post, because it has a lot of features specific for Windows environment.
The features I'd like to mention are:
- Installer improvements in Mac OS X
The new installer can now configure some kernel parameters which are needed to take full advantage of IDS. Just recently a fellow IIUG mailing list user was asking about some issues. He tried the IDS 11.50.xC1 installation and hit some issues. After repeating it with IDS 11.50.xC2 everything was ok with the default instance setup
- Reconfiguration of the Connection Manager without restart
The new version of Connection Manager allows it's reconfiguration without restart. Just use the -r option. This is a nice feature, since the purpose of the Connection Manager is to collaborate in the increase of the availability of your cluster. So the need to restart it to change it's configuration was annoying. Nevertheless, you should always use more than one instance of the connection manager, so if you need to change it's configuration you should change one instance at a time. Doing this allows you to keep you connection infra-structure answering requests while you go through your CM instances, changing it's configuration
- Several improvements in the Enterprise Replication facility
You can check Guy's post and the release notes to check all the changes. They are well covered there
- Limiting the number of sessions that can connect to IDS
Once in a while a customer asks me if we have any way to control the maximum number of sessions that can connect to one instance... I usually ask why, and if they can control it on the application side. Sometimes I wonder I they need this, and sometimes they remember me that the most famous IDS competitor has this "feature". I even saw situations where they need to recycle an instance to increase it... Well, I must confess that I've seen situations (specially with Java applications using application servers and connection pools) where the application starts to fire an incredible number of connections (sometimes because there are problems in the database server). In these situations it's a good idea to have a limit of sessions. And after 11.50.xC2 we have a new parameter that allows this. It's called LIMITNUMSESSIONS. If you don't define it, the server ignores the limit. If you define it then the server only allows the specified number of sessions. After that number is reached the new connections will be refused and an error code (-25571) received.
The best aspect of this feature is that (as many new features) it allows for easy online reconfiguration using onmode -wm and onmode -wf
Also note that any DBSA user will be allowed to connect even if the maximum connections that we specify was already reached
- New format for backup/restore filters
The relatively new feature that allows us to put a whole backup through a custom filter program (BACKUP_FILTER and RESTORE_FILTER parameters) were changed to use another format for backup. This is pretty transparent to the user/dba, but you have to keep in mind that you can't restore a backup made in previous versions with this new release (and vice-versa). So the real impact of this is that you must keep a record of which version you used to make your backups if you use this functionality
- New BTSCANNER option to specify the compression level
There is a new option in the BTSCANNER parameter that allows us to define the level of data on the pages that trigger the compression of index pages. This can also be changed dynamically using onmode -C compression
and an SQL API command SET INDEX COMPRESSION
- Server specific audit configuration file
I recently wrote in the Audit and Role Separation article that one of the problems was that the changes we made using the onaudit utility were written to an adtcfg.
file but the instance alwasy looked at the adtcfg file. Well, finally it's fixed, and now the changes and the server look at the adtcfg. file
Well, if you already played with IDS 11.50.xC1 and redirected writes you probably know that the parameter to activate the redirected writes was called REDIRECTED_WRITES. Well, the parameter changed it's name. It's now called UPDATABLE_SECONDARY. This is not clearly stated in the release notes (although it's mentioned in the documentation notes). Eric Herbert and I hit this issue, so please be warned if you're going to play with redirected writes
- COMMITTED READ/LAST COMMITTED on HDR and RSS servers
Another feature that may be very useful and it's not well explained in the release notes. With this release, you can use the COMMITTED READ and the LAST COMMITTED isolation level on the HDR and RSS servers. This is a big change, since we all expect these servers to accept only DIRTY READ. Also, these isolation levels were already supported in SDS servers. The only thing you have to do it to activate the redirected writes. This will start a component called the lock manager that is needed to support these two isolation levels. So things like onmode -k start to make sense and be useful on secondary servers.
Obviously the default isolation level is still the dirty read (even with redirecte writes active)
- Other features...
There are several other features, like improvements in the Open Admin Tool, longer (32K) return strings from several string related functions and subquery support in UPDATE and DELETE statements