Appendix C - System Capacities

The following is a detailed list of the capacities for the different components in DBISAM. Unless where noted all capacities are absolute and not dependent upon the underlying operating system or network.

Capacity

Details

# of BLOB Fields in a Table	The maximum number of BLOB fields in a table is 128.
# of Decimal Places in a BCD Field	The maximum number of decimals places in a BCD field is 4.
# of Fields in Table	The maximum number of fields in a table is 1024.
# of Fields in an Index Key	The maximum number of fields in an index key is 128.
# of Indexes in a Table	The maximum number of primary indexes in a table is 1. The maximum number of secondary indexes in a table is 30.
# of Open BLOBs in a Table	The maximum number of open BLOBs in a table is 128.
# of Open Tables	The maximum number of open tables is only limited by the available memory constraints of the operating system or hardware. DBISAM has a limit of 4096 tables per database, but a single application can open the same table in the same database many times as well as open many tables from other databases.
# of Records in a Table	The maximum number of records in a table is 1 billion.
# of Records in a Transaction	The maximum number of records in a single transaction is only limited by the available memory constraints of the operating system or hardware.
# of Tables in a Database	The maximum number of tables in a database is 4096 tables.
Size Of Database Names	The maximum size of a database name is 60 bytes.
Size Of Field Constraint	The maximum size of a field constraint expression is 100 bytes.
Size Of Field Descriptions	The maximum size of a field description is 100 bytes.
Size Of Field Names	The maximum size of a field name is 60 bytes.
Size Of Index Names	The maximum size of an index name is 60 bytes.
Size Of Physical Table Files	The maximum size of the physical files that make up a table - <TableName>.dat for data, <TableName>.idx for indexes, and <TableName>.blb for BLOBS, is 128,000,000,000 bytes for each file.
Size Of Table Descriptions	The maximum size of a table description is 100 bytes.
Size Of Table Names	The maximum size of a table name is 60 bytes.
Size of BLOB Blocks	The minimum BLOB block size is 64 bytes and the maximum BLOB block size is 64 kilobytes.
Size of BLOB Fields	The maximum length of a BLOB field is 2 gigabytes.
Size of In-Memory Tables	The maximum length of an in-memory table is only limited by the available memory constraints of the operating system or hardware.
Size of Index Keys	The maximum size of an index key is 4096 bytes. The index key length is not an exact sum of the length of the fields present in the index key. The proper way to calculate the index key length is as follows: For primary indexes the calculation is: ((Sum of field sizes) + Number of Fields in Index Key For secondary indexes the calculation is: ((Sum of field sizes) + Number of Fields in Index Key + 4 The extra bytes for the number of fields are the NULL flags used to order the index keys properly based upon whether they are NULL or not. The additional four bytes for secondary indexes is used to store a unique record ID which is essential for proper bookmark support. The length of string fields in index keys includes the null terminator character. For example, if a string field has a length of 15 then its length in an index key would be 16.
Size of Index Pages	The minimum index page size is 1024 bytes and the maximum index page size is 16 kilobytes.
Size of Records	The maximum record size is 65280 bytes.
Size of String Fields	The maximum length of a string field is 512 bytes. This figure does not include a NULL terminator character. The NULL terminator character is handled internally.

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