Table of Contents

Search

  1. preface
  2. Introduction
  3. Defining a System
  4. Flattening IDTs
  5. Link Tables
  6. Loading a System
  7. Static Clustering
  8. Simple Search
  9. Search Performance
  10. Miscellaneous Issues
  11. Limitations
  12. Error Messages

Limitations

Limitations

IIR design and host DBMS impose some limits:

Database

  • Only one field per file with a format B(inary) can exceed 255 bytes in length.
  • C(haracter) fields can not exceed 2000 bytes.
  • There is a maximum of 255 fields per file.
  • File-name length is limited to 23 bytes.
  • Index-name length is limited to 22 bytes.
  • IDX Key is limited to 255 bytes.
  • A maximum of 4G - 1 rows per IDT.
  • LOB columns are limited to 16 MB.

Object Names

Object names (tables, indexes, columns, functions) follow the rules of the host DBMS, with the following additional restrictions:
  • identifiers must not exceed 32 bytes in length
  • MS-SQL: Only regular identifiers are supported (up to 32 bytes in length)

IDENTITY functions (MS-SQL Server)

MS-SQL Server provides a function named
@@IDENTITY
that returns the identity value generated by the last performed
INSERT
,
SELECT INTO
or bulk copy statement.
For a synchronized system, if any source data tables contain identity columns, the
@@IDENTITY
function is not safe to use for the purpose of returning the last updated row from any of these source data tables. This is due to IIR using an identity column in the
IDS_UPD_SYNC_TXN
table.
Whenever a source table row is updated, a trigger will fire and insert a row into
IDS_UPD_SYNC_TXN
. Therefore the
@@IDENTITY
function will return the identity of the last row inserted into
IDS_UPD_SYNC_TXN
, not the identity of the last updated source table row.
MS SQL 2000 provides two new functions for handling this:
  • SCOPE_IDENTITY()
    will return the last
    IDENTITY
    value inserted into an
    IDENTITY
    column in the same scope. Two statements are in the same scope if they are in the same stored procedure, function, or batch. Since it returns values inserted only within the current scope, it will not report on the
    IDS_UPD_SYNC_TXN
    table.
  • IDENT_CURRENT
    (’Table name’) will return the last
    IDENTITY
    value generated for the specified table in any session and any scope. Since it returns values inserted only in the specified table, it will not report on the
    IDS_UPD_SYNC_TXN
    table.
We recommend that one of these functions be used instead of the
@@IDENTITY
function.

Synchronizer

  • Maximum of 36 PK fields per IDT.
  • Each PK field value must be less than 1000 bytes in length
  • The combined length of PK field names and PK field values can not exceed 2000 bytes.

Servers

  • Maximum of 1024 TCP/IP connections per Server
  • Maximum of 4096 database connections per Database Module (
    ssadbm.dll
    ).

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