Multi-resident of Informix

I. Multi-resident

Multiple Residency) means to run Multiple OnLine instances on the same host. Each OnLine instance has and manages its own processes, shared memory, and disk space. Multi-resident does not mean to install OnLine software to multiple different directories. Both OnLine5.0, Online7.x, and IDS support multiple resident statuses, and data inventory servers of different versions can reside on the same host.

Since multiple databases can be created on an OnLine database server, you do not need to use multiple resident services to meet various data management requirements. However, to meet special requirements, it may be found that the use of multiple resident can bring a lot of convenience. For example, the OnLine archive and logical log files are for the entire database server and can only be created for a dbspace in OnLine7.1), rather than for the database, in order to separate some databases for management and use, you can consider using multiple resident services.

In short, the use of multi-resident can have the following advantages:
1. Separate the production environment from the development environment;
2. Isolate important databases;
3. Test Distributed Data transactions on a single host.

The reason why multiple resident services can run independently without mutual interference is that these OnLine instances use different shared memory areas, disk space, and other resources. The OnLine administrator must specify different configuration files for each OnLine instance through the TBCONFIG or ONCONFIG environment variables), and specify duplicate values for the following parameters in the configuration file:

1. RVERNUM
By setting different SERVERNUM and OnLine, different shared memory keyword values are calculated and applied for different shared memory segments from the UNIX operating system. The OnLine process and customer application will also attach or find the required shared memory based on this value.

2. ROOTPATH and ROOTOFFSET
The above two parameters are combined to uniquely determine the initial chunk of the root dbspace, so that different OnLine instances use different disk space. If the same ROOTPATH is used, calculate the exact value of the second OnLine roottoffset based on the value of the previous ROOTSIZE)

3. ERVERNAME and DBSERVERALLASES (OnLine7)
These two parameters allow multiple database servers to connect to each other by name. In OnLine5.0, only one DBSERVERNAME parameter is provided and does not work if the INFORMIX-STAR connection product is not installed.

4. MSGPATH
This parameter differentiates the running status tracking residences of different OnLine instances.
5. IRRORPATH and MIRROROFFSET
If the image is used for root dbspaces, the disk space defined by the preceding two parameters must not be reused on both servers.

Ii. Use of multiple resident services

The method of using multi-resident is to configure another database server After configuring one database server. The procedure for configuring another server is the same as before. Note that they use their respective configuration files. Different values must be specified for some environment variables and configuration parameters. The following uses OnLine7.1 as an example to describe how to configure another OnLine account:

1. Informix User Registration: copy a new ONCONFIG file, set the environment variables, and set the new ONCONFIG and INFORMIXSERVER environment variables. Point the ONCONFIG environment variable to the new ONCONFIG configuration file. The new ONCONFIG file name best reflects the SERVER's purpose and serial number SERVERNUM), such as onconfig. dev14, indicates that the database SERVER is used for the development environment and the SERVER used is 14.

2. Use the onconfig configuration file that is updated by editing and onmonitor. The values of the following parameters should be different from those in other OnLine configuration files: SERVERNUM, ROOTPATH, ROOTOFFSET, DBSERVERNAME, and MSGPATH; if the image is used, there are mirror path and MIRROFFSET.

3. allocate disk space and check whether the path, owner, and permissions of the original disk device or UNIX File allocated to OnLIne meet the requirements.

4. Modify the connection file and set the new dbservername in $ INFORMIXDIR/etc/sqlhosts. If necessary, set the network service information in files such as/etc/services.

5. Use the oninit-I command to initialize the disk space. Be sure to use different environment variables.

6. If you use the onarchive backup tool, configure onarchive. onarchive uses onconfig. arc as the configuration file and oper_deflt.arc as the default file for the operator command. You can set the ARC_CONFIG and ARC_DEFAULT environment variables to specify a new file name to replace the preceding two files.

7. For other work, you can ask the operating system administrator to put the OnLine commands to the script for automatic on/off. When starting or disabling multiple OnLine services, in addition to the INFORMIXDIR and PATH environment variables that have been set, you should change the ONCONFIG and INFORMIXSERVER variables.

When multiple OnLine instances run normally, if the new OnLine instance is the default database server, the user's INFORMIXSERVER environment variable should be reset to the new dbservername. You can use the SQL statement CONNECT or DATABASE in your application to directly CONNECT to the specified server.