Determines the number of tables that can be opened in a given local TSR or VTS-TSR. (With the possibility of creating a TSR of up to 2G in size, there can be a great variation in how many tables will actually be in a TSR at any time.) If the value of the MAXNMTAB is not set by the user (or is set to zero) then a default value is calculated.
If an attempt is made to open more tables than is indicated by MAXNMTAB, an error code of 20 will be given: The maximum number of tables has been exceeded. Check MAXNMTAB.
This option applies to the TSR created by this region/job and all users accessing it.
This option can be specified for all tableBASE interfaces.
User sets the value of MAXNMTAB
To optimize the memory required for system overhead, the user may choose to set the value of MAXNMTAB rather than use the default value. MAXNMTAB can be set to any integer, zero or greater. However, if MAXNMTAB is set to a value greater than the default for the given TSR size, the default is used and the user is notified with a warning message.
After the user sets the value of MAXNMTAB, memory is allocated and an index is created that contains enough entries to support the maximum number of tables indicated. Additional memory is allocated as tables are opened. This memory is reused as tables are closed and new tables opened. This approach keeps the system overhead in line with the number of tables that are opened.
The calculation of the default value of MAXNMTAB
If the user does not set the value MAXNMTAB or the value is zero, the tableBASE software calculates the default value based on the size of the TSR. Each table in the TSR occupies a minimum of 4K pages. The maximum possible number of tables is 51,455, for a 2G TSR; the default, when unspecified is one table for every 4K page in the TSR.