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Don Burleson Blog 







Maximum Oracle Limits

Oracle Database Tips by Donald BurlesonFebruary 16, 2015

Question:  I have a job interview and I am expected to memorize the maximum limits for Oracle tables, indexes files ad tablespace.  Why is it important to know the maximum values for these items?

Answer:  I have been a DBA for more than 25 years and I have never hit the huge upper limits for Oracle tables, and the maximum values for tablespace and data files are nothing more than idle exercise. 

However, here are the maximum values for some of the most important Oracle structures:


Maximum Limit

Maximum advanced queuing processes per instance


Maximum background process slave processes


Maximum blocks per file

222 - 1 blocks

Maximum columns per bitmap index

30 columns maximum

Maximum columns per b-tree index

32 columns

Maximum columns per table


Maximum database block size

32k except for Windows at 16k

Maximum files per database

65,533 files, except for Windows

Maximum files per tablespace

1,022 files

Maximum global cache service processes


Maximum index column size

75% of the database block size less minor overhead

Maximum job queue processes per instance


Maximum length of linear partitioning key

4 KB - overhead

Maximum number of columns in partition key

16 columns

Maximum number of partitions per table/ index

1,024,000 - 1

Maximum number of roles


Maximum number of users


Maximum sessions per instance

32k sessions

Maximum table/index extents

 (2GB * block size)

Maximum tables per cluster

32 tables

Maximum tablespaces per database

64k tablespaces




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