
System Architecture 2-53
Shared-Memory Internal Tables
Eachtblspacetableentryincludesheaderinformationabout 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 on page 2-104.)
The number of entries inthe tblspacetable is equal to themaximum number
ofopentblspacespermittedinthisOnLinesystem,specifiedasTBLSPACES in
the configuration file. If a user process attempts to open an additional table
after all entriesareused,an error is returned. A singleuserprocessis limited
to 32 concurrent table locks.
Each entry in the tblspace table occupies 232 bytes.
Referto page 3-85for information about monitoring tblspaces usingtbstat -t.
The upper limit for the maximum number of tblspaces (specified as
TBLSPACES in the configuration file) is 32,000. The lower boundary for
TBLSPACES is the number of user processes(specified as USERS in the config-
uration file) multiplied by 10. The minimum value for TBLSPACES is 10 per
user. This minimum also must be greater than the maximum number of
tables in any one database, including the system catalog tables, plus 2. (This
minimum is required to permit OnLine to execute a DROP 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 ofhash valuesis thelargestpower of twothatis less than
the value specified by the expression (TBLSPACES divided by 4).
Each entry in the lock hash table occupies four bytes.
Refer to page 2-46 for an explanation of the hash table.
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