2 gb or not 2gb file limits in oracle

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2Gb or Not 2Gb - File limits in Oracle [ID 62427.1]
Modified 29-SEP-2010 Type BULLETIN Status ARCHIVED
Applies to:
Oracle Server - Enterprise Edition - Version: 7.0.16.0 to 8.1.7.4 - Release: 7.0 to 8.1.7
Information in this document applies to any platform.
Purpose
This document describes "2Gb" issues. It gives information on why 2Gb is a
magical number and outlines the issues you need to know about if you are
considering using Oracle with files larger than 2Gb in size. It also
looks at some other file related limits and issues.
Articles giving port specific limits are listed in the last section.
Topics covered include:
Why is 2Gb a Special Number ?
Why use 2Gb+ Datafiles ?
Export and 2Gb
SQL*Loader and 2Gb
Oracle and other 2Gb issues
Port Specific Information on "Large Files"
Scope and Application
This document has a Unix bias as this is where most of the 2Gb issues arise
but there is information relevant to other (non-unix) platforms.
Note: Questions regarding application specific issues (e.g., Concurrent Manager
in Oracle E-Business Suite R12.1.2 on OEL5-64-bit.) and file size limitations
will need to be addressed with the specific application team and are beyond the
scope of this document.
2Gb or Not 2Gb - File limits in Oracle
Why is 2Gb a Special Number?
Many CPU's and system call interfaces (API's) in use today use a word
size of 32 bits. This word size imposes limits on many operations.
In many cases the standard API's for file operations use a 32-bit signed
word to represent both file size and current position within a file (byte
displacement). A 'signed' 32bit word uses the top most bit as a sign
indicator leaving only 31 bits to represent the actual value (positive or
negative). In hexadecimal the largest positive number that can be
represented in in 31 bits is 0x7FFFFFFF , which is +2147483647 decimal.
This is ONE less than 2Gb.
Files of 2Gb or more are generally known as 'large files'. As one might
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expect, problems can start to surface once you try to use the number
2147483648 or higher in a 32bit environment. To overcome this problem
recent versions of operating systems have defined new system calls which
typically use 64-bit addressing for file sizes and offsets. Recent Oracle
releases make use of these new interfaces but there are a number of issues
one should be aware of before deciding to use 'large files'.
Another "special" number is 4Gb. 0xFFFFFFFF in hexadecimal can be
interpreted as an UNSIGNED value (4294967295 decimal) which is one less
than 4Gb. Adding one to this value yields 0x00000000 in the low order
4 bytes with a '1' carried over. The carried over bit is lost when using
32bit arithmetic. Hence 4Gb is another "special" number where problems
may occur. Such issues are also mentioned in this document.
What does this mean when using Oracle?
The 32bit issue affects Oracle in a number of ways. In order to use large
files you need to have:
1. An operating system that supports 2Gb+ files or raw devices
2. An operating system which has an API to support I/O on 2Gb+ files
3. A version of Oracle which uses this API
Today most platforms support large files and have 64bit APIs for such files.
Releases of Oracle from 7.3 onwards usually make use of these 64bit APIs but
the situation is very dependent on platform, operating system version and
the Oracle version. In some cases 'large file' support is present by
default, while in other cases a special patch may be required.
At the time of writing there are some tools within Oracle which have not
been updated to use the new API's, most notably tools like EXPORT and
SQL*LOADER, but again the exact situation is platform and version specific.
Why use 2Gb+ Datafiles?
In this section we will try to summarise the advantages and disadvantages
of using "large" files / devices for Oracle datafiles:
Advantages of files larger than 2Gb:
On most platforms Oracle7 supports up to 1022 datafiles.
With files < 2Gb this limits the database size to less than 2044Gb.
This is not an issue with Oracle8 and higher which supports many more files.
(Oracle8 supported 1022 files PER TABLESPACE).
In reality the maximum database size in Oracle7 would be less than
2044Gb due to maintaining separate data in separate tablespaces.
Some of these may be much less than 2Gb in size. Larger files
allow this 2044Gb limit to be exceeded.
Larger files can mean less files to manage for smaller databases.
Less file handle resources required.

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Disadvantages of files larger than 2Gb:
The unit of recovery is larger. A 2Gb file may take between 15 minutes
and 1 hour to backup / restore depending on the backup media and
disk speeds. An 8Gb file may take 4 times as long.
Parallelism of backup / recovery operations may be impacted.
There may be platform specific limitations - Eg: Asynchronous IO
operations may be serialised above the 2Gb mark.
As handling of files above 2Gb may need patches, special configuration
etc.. there is an increased risk involved as opposed to smaller files.
Eg: On certain AIX releases Asynchronous IO serialises above 2Gb.
Important points if using files >= 2Gb
Check with the OS Vendor to determine if large files are supported
and how to configure for them.
Check with the OS Vendor what the maximum file size actually is.
Check with Oracle support if any patches or limitations apply
on your platform , OS version and Oracle version.
Remember to check again if you are considering upgrading either
Oracle or the OS in case any patches are required in the release
you are moving to.
Make sure any operating system limits are set correctly to allow
access to large files for all users.
Make sure any backup scripts can also cope with large files.
Note that there is still a limit to the maximum file size you
can use for datafiles above 2Gb in size. The exact limit depends
on the DB_BLOCK_SIZE of the database and the platform. On most
platforms (Unix, NT, VMS) the limit on file size is around
4194302*DB_BLOCK_SIZE.
See the details in the Alert in which describes
problems with resizing files, especially to above 2Gb in size.
Important notes generally
Be careful when allowing files to automatically resize. It is
sensible to always limit the MAXSIZE for AUTOEXTEND files to less
than 2Gb if not using 'large files', and to a sensible limit
otherwise. Note that due to it is possible to specify
an value of MAXSIZE larger than Oracle can cope with which may
result in internal errors after the resize occurs. (Errors
typically include ORA-600 [3292])
On many platforms Oracle datafiles have an additional header
block at the start of the file so creating a file of 2Gb actually
requires slightly more than 2Gb of disk space. On Unix platforms

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the additional header for datafiles is usually DB_BLOCK_SIZE bytes
but may be larger when creating datafiles on raw devices.
2Gb related Oracle Errors:
These are a few of the errors which may occur when a 2Gb limit
is present. They are not in any particular order.
ORA-01119 Error in creating datafile xxxx
ORA-27044 unable to write header block of file
SVR4 Error: 22: Invalid argument
ORA-19502 write error on file 'filename', blockno x (blocksize=nn)
ORA-27070 skgfdisp: async read/write failed
ORA-02237 invalid file size
KCF:write/open error dba=xxxxxx block=xxxx online=xxxx file=xxxxxxxx
file limit exceed.
Unix error 27, EFBIG
Export and 2Gb
2Gb Export File Size
At the time of writing most versions of export use the default file
open API when creating an export file. This means that on many platforms
it is impossible to export a file of 2Gb or larger to a file system file.
There are several options available to overcome 2Gb file limits with
export such as:
- It is generally possible to write an export > 2Gb to a raw device.
Obviously the raw device has to be large enough to fit the entire
export into it.
- By exporting to a named pipe (on Unix) one can compress, zip or
split up the output.
See: "Quick Reference to Exporting >2Gb on Unix"
- One can export to tape (on most platforms)
See "Exporting to tape on Unix systems"
(This article also describes in detail how to export to
a unix pipe, remote shell etc..)
- Oracle8i allows you to write an export to multiple export
files rather than to one large export file.
Other 2Gb Export Issues
Oracle has a maximum extent size of 2Gb. Unfortunately there is a problem
with EXPORT on many releases of Oracle such that if you export a large table
and specify COMPRESS=Y then it is possible for the NEXT storage clause
of the statement in the EXPORT file to contain a size above 2Gb. This
will cause import to fail even if IGNORE=Y is specified at import time.
This issue is reported in and is alerted in

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An export will typically report errors like this when it hits a 2Gb
limit:
. . exporting table BIGEXPORT
EXP-00015: error on row 10660 of table BIGEXPORT,
column MYCOL, datatype 96
EXP-00002: error in writing to export file
EXP-00002: error in writing to export file
EXP-00000: Export terminated unsuccessfully
There is a secondary issue reported in which indicates that
a full database export generates a CREATE TABLESPACE command with the
file size specified in BYTES. If the filesize is above 2Gb this may
cause an ORA-2237 error when attempting to create the file on IMPORT.
This issue can be worked around be creating the tablespace prior to
importing by specifying the file size in 'M' instead of in bytes.
indicates a similar problem.
Export to Tape
The VOLSIZE parameter for export is limited to values less that 4Gb.
On some platforms may be only 2Gb.
This is corrected in Oracle 8i. describes this problem.
SQL*Loader and 2Gb
Typically SQL*Loader will error when it attempts to open an input
file larger than 2Gb with an error of the form:
SQL*Loader-500: Unable to open file (bigfile.dat)
SVR4 Error: 79: Value too large for defined data type
The examples in can be modified to for use with SQL*Loader
for large input data files.
Other 2Gb issues
This sections lists miscellaneous 2Gb issues:
- From Oracle 8.0.5 onwards 64bit releases are available on most platforms.
An extract from the 8.0.5 README file introduces these - see
- DBV (the database verification file program) may not be able to scan
datafiles larger than 2Gb reporting "DBV-100".
- "DATAFILE ... SIZE xxxxxx" clauses of SQL commands in Oracle must be
specified in 'M' or 'K' to create files larger than 2Gb otherwise the
error "ORA-02237: invalid file size" is reported. This is documented
in .
- Tablespace quotas cannot exceed 2Gb on releases before Oracle 7.3.4.
Eg: ALTER USER QUOTA 2500M ON
reports
ORA-2187: invalid quota specification.
This is documented in .
The workaround is to grant users UNLIMITED TABLESPACE privilege if they

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need a quota above 2Gb.
- Tools which spool output may error if the spool file reaches 2Gb in size.
Eg: sqlplus spool output.
- Certain 'core' functions in Oracle tools do not support large files
- The UTL_FILE package uses the 'core' functions mentioned above and so is
limited by 2Gb restrictions Oracle releases which do not contain this fix.
is a PL/SQL package which allows file IO from within
PL/SQL.
Port Specific Information on "Large Files"
Below are references to information on large file support for specific
platforms. Although every effort is made to keep the information in
these articles up-to-date it is still advisable to carefully test any
operation which reads or writes from / to large files:
Platform See
~~~~~~~~ ~~~
AIX (RS6000 / SP)
Digital Unix
Sequent PTX
Sun Solaris
Windows NT Maximum 4Gb files on FAT
Theoretical 16Tb on NTFS
** See before using large files
on NT with Oracle8
*2 There is a problem with DBVERIFY on 8.1.6
See
*3 There is a problem with 8.1.6 / 8.1.7
where an autoextend to 4Gb can
cause a crash - see
Related
Products
Oracle Database Products > Oracle Database > Oracle Database > Oracle Server - Enterprise Edition
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