The purpose of the SYS% facility is to provide a method of managing system data sets with SMS in a multi-host environment. Each system requires duplicate system data sets (data sets with the high-level qualifier SYS1).

Because SMS requires uniquely named data sets, you normally would not be able to access the system data sets for one system from another system. However, you might need to update one system's SYS1 data sets from a different system.

The SYS% facility allows you to do this by permitting access to system data sets with alias names. The alias names have SYS for the first three characters, followed by another character that is not 1 (for example, SYSA). You use the alias to first orient the search to the appropriate master catalog, which is then searched for the requested system data set.

As an example, consider a complex with two systems, each using SMS, called SYSTEMA and SYSTEMB. To connect the systems, the master catalog of each system is defined as a user catalog in the master catalog of the other system. This can be seen in Figure 1.

Figure 1. Master Catalogs of Connected SMS Systems. The pointers from MASTCAT.B to MASTCAT.A are not shown, to make the diagram clearer. Catalog entries are enclosed in parentheses.

In this example, MASTCAT.A is defined with the alias SYSA in MASTCAT.B; and MASTCAT.B is defined with the alias SYSB in MASTCAT.A. Each catalog contains a pointer to a different SYS1.LINKLIB system data set. If a job addresses the data set SYS1.LINKLIB, the SYS1.LINKLIB that is allocated depends on which system is running the job.

In order for a job running on SYSTEMA to access the SYS1.LINKLIB cataloged in MASTCAT.B on SYSTEMB, that job must orient itself to the other master catalog. This can be done by using the SYS% facility and the alias defined for the other master catalog.

If the SYS% facility is active, a job running on SYSTEMA can address SYSB.LINKLIB. Because SYSB is an alias of MASTCAT.B, MASTCAT.B is searched for a data set named SYSB.LINKLIB. Because one is not found, MASTCAT.B is again searched, only this time for SYS1.LINKLIB, which is found. The job then uses the SYS1.LINKLIB cataloged in MASTCAT.B, even though the job ran on SYSTEMA, and there is a SYS1.LINKLIB cataloged in SYSTEMA's master catalog.

If the alias is not defined (if you specify an alias that does not exist), the SYS% conversion routine will resolve to the current system.

Example: If you specify SYSX.LINKLIB on SYSTEMA, and SYSX is not defined as an alias to another system, then the request would go to SYS1.LINKLIB on SYSTEMA.

Make sure that you have located the correct system SYS1 data set. Also, if you specify SYSX.LINKLIB on SYSTEMA, and SYSX is defined as an alias to another system but the SYS1.LINKLIB does not exist on SYSTEMB, the request would go to SYS1.LINKLIB on SYSTEMA.