Increases in the Physical Size of Your Database

The addition of new fields during the process of creating a Design Master database imposes two limitations on your tables:

• Microsoft Jet allows a maximum of 2048 bytes (not counting Memo or OLE Object fields) in a record. Replication uses a minimum of 28 bytes to store unique identifiers and information about changes to the record. If the record contains either Memo or OLE Object fields, replication uses an additional 4 bytes for each of those fields. The total number of bytes available in a record in a replicated table can be calculated as follows:

  2048 bytes
   – 28 bytes for replication overhead
   – (4 bytes * the number of Memo fields)
   – (4 bytes * the number of OLE Object fields)
  = the maximum number of bytes available

• Microsoft Jet allows a maximum of 255 fields in a table, of which at least three fields are used by replication. The total number of fields available in a replicated table can be calculated as follows:

  255 fields
   – 3 system fields
   – the number of Memo and OLE Object fields
  = the number of fields available

Few well-designed applications use all the available fields in a table or characters in a record. However, if you have a large number of Memo fields or OLE Object fields in your table, you should be aware of your remaining resources.

In addition to setting limits on the available number of characters and fields, Microsoft Jet replication also limits the number of nested transactions allowed. You can have a maximum of seven nested transactions in a nonreplicable database, but a replicated database can have a maximum of six nested transactions.

Just as the addition of three new fields to your tables adds to the size of each record, the addition of new system tables also adds to the size of your database. Many of these new tables contain only a few records, but some of the new tables can grow significantly, depending upon the frequency of synchronization between replicas.

The size of your database file is significant for two reasons:

• Microsoft Jet supports files up to a maximum of 1 GB in size, but many users have limited space available on their hard disks and the creation of a replicable database that is larger than the original file could exceed available disk space.
  
  
• If you choose to make a backup copy of the nonreplicable form of your database, you must have sufficient space on your hard disk for both the replicated database and the backup copy.