Limitations of the Oracle Database System

Definition

The Oracle database has the limitations described in this section. The parameters MAXEXTENTS, DBFILES, and MAXDATAFILES are discussed.

Use

You need to be aware of the limitations described below when you are:

·        Reorganizing Tables with BR*Tools

·        Extending a Tablespace with BR*Tools

If you use locally managed tablespaces (LMTS) with autoallocate, you can avoid the situation where your tables have a large number of small extents.

Structure

·        Maximum number of extents per table or index – MAXEXTENTS

For older installations with dictionary managed tablespaces, we recommend setting MAXEXTENTS to UNLIMITED.

For new installations with LMTS, the autoallocate feature optimizes extent growth for tablespaces.

·        Maximum number of files per database – DB_FILES

Ў        Soft limit

The SAP software value for DB_FILES is 254.

The database system only supports a specific number of data files in the database, depending on the host system, and this is specified by the DB_FILES parameter in the init<DBSID>.ora profile.  If your database approaches this limit, you can reduce the number of data files by reorganizing tablespaces that have more than one file. However, this is not likely to occur with a limit of 254 files for not very large databases.

Ў        Hard limit

The hard limit for DB_FILES depends on the operating system but is usually 1022 per tablespace and 65533 per database.

DB_FILES can be increased to the value of MAXDATAFILES, the value of which was specified when the database was created. MAXDATAFILES itself must be less than the permissible maximum number of open files supported by the operating system. The default value for MAXDATAFILES is also 254.

Do not regularly reorganize the database to reduce the number of data files. This is because the possible number of data files is large, so is not normally reached.