Making performance decisions for names service

You, the system programmer, can change the QCASTAT variable for the names service to indicate whether the names directory tables are to remain open after they are initially opened or are closed after each use and reopened when needed again. For information about how to change QCASTAT, see Table 1. Information Center Facility users can make the same choice on a panel in the names services. By default, the names directories are open and kept in virtual storage only until users are finished accessing them.

Specifying that the directories remain open:

Reduces the I/O overhead of opening and closing the directories each time a user accesses them.
Simplifies directory processing by applications that use the names service because the applications do not have to open and close the tables each time they access them.

However leaving the directories open:

Requires additional user storage above 16 MB in virtual storage. To estimate the amount of storage needed for the names service, see Storage required by names service.
Prevents users from always obtaining the directory they want:
- Users may not obtain the latest changes the administrator makes to the master directory. To obtain the latest changes, users must close and open the directory.
- When users request just the private directory, they receive both the private and the merged directory.
- When users request the master directory, they may receive the merged directory, and vice versa.

Note: If your system is storage-constrained, do not specify that the names tables are to remain open because leaving them open could degrade performance.