System Architecture 2-53
Shared-Memory Internal Tables
Eachtblspace table entry includes header information about the tblspace, the
tblspace name, and pointers to the tblspace tblspace in the root dbspace on
disk. (Do not confuse the shared-memory active tblspace table with the
tblspace tblspace, which is described onpage 2-104.)
Thenumber of entries in the tblspace table is equal to the maximum number
ofopen tblspaces permitted in this OnLine system, specified as TBLSPACES in
the configuration file. If a user process attempts to open an additional table
afterall entries are used, an error is returned. A single user process is limited
to 32 concurrent table locks.
Each entry in the tblspace table occupies 232 bytes.
Referto page 3-85 for information about monitoring tblspaces using tbstat -t.
The upper limit for the maximum number of tblspaces (specified as
TBLSPACES in the configuration file) is 32,000. The lower boundary for
TBLSPACESis the number of user processes (specified as USERS in the config-
uration file) multiplied by 10. The minimum value forTBLSPACES is 10 per
user. This minimum also must be greater than the maximum number of
tablesin any one database, including the system catalog tables, plus 2. (This
minimum is required to permit OnLine to execute aDROP DATABASE
statement.)
The default value is 200.
The number of entries in the tblspace hash table is based on the number of
allocated tblspaces (specified as TBLSPACES in the configuration file). The
maximumnumber of hash values is the largest power of two that is less than
the value specified by the expression (TBLSPACES divided by 4).
Each entry in the lock hash table occupies four bytes.
Refer topage 2-46 for an explanation of the hash table.