For those who find it difficult to find in Reference Manuals
Physical Database Limits
Logical Database LimitsCode:Item Type of Limit Limit Value Database Block Size Minimum 2048 bytes; must be a multiple of operating system physical block size Maximum Operating system dependent; never more than 32 KB Database Blocks Minimum in initial 2 blocks extent of a segment. Maximum per datafile Platform dependent; typically 222-1 blocks Controlfiles Number of control files 1 minimum; 2 or more (on separate devices) strongly recommended Size of a control file Dependent on operating system and database creation options; maximum of 20,000 x (database block size) Database files Maximum per tablespace Operating system dependent; usually 1022 Maximum per database 65533 May be less on some operating systems Limited also by size of database blocks and by the DB_ FILES initialization parameter for a particular instance Database extents Maximum 2 GB, regardless of the maximum file size allowed by the operating system Database file size Maximum Operating system dependent. Limited by maximum operating system file size; typically 222 or 4M blocks MAXEXTENTS Default value Derived from tablespace default storage or DB_BLOCK_ SIZE initialization parameter Maximum Unlimited Redo Log Files Maximum number of Limited by value of LOG_FILES initialization parameter logfiles or MAXLOGFILES parameter in the CREATE DATABASE statement Control file can be resized to allow more entries; ultimately an operating system limit Maximum number of Unlimited logfiles per group Redo Log File Size Minimum size 50 KB Maximum size Operating system limit; typically 2 GB Tablespaces Maximum number per 64 K database Number of tablespaces cannot exceed the number of database files, as each tablespace must include at least one file
Process and Runtime LimitsCode:Item Type of Limit Limit Value GROUP BY clause Maximum length The GROUP BY expression and all of the nondistinct aggregates functions (for example, SUM, AVG) must fit within a single database block. Indexes Maximum per table Unlimited total size of indexed column 75% of the database block size minus some overhead Columns Per table 1000 columns maximum Per index (or clustered index) 32 columns maximum Per bitmapped index 30 columns maximum Constraints Maximum per column Unlimited Subqueries Maximum levels of subqueries Unlimited in the FROM clause of the top-level in a SQL statement query 255 subqueries in the WHERE clause Partitions Maximum length of linear 4 KB - overhead partitioning key Maximum number of columns 16 columns in partition key Maximum number of partitions 64 K-1 partitions allowed per table or index Rollback Segments Maximum number per database No limit; limited within a session by the MAX_ ROLLBACK_SEGMENTS initialization parameter Rows Maximum number per table Unlimited SQL Statement Length Maximum length of statements 64 K maximum; particular tools may impose lower limits Stored Packages Maximum size PL/SQL and Developer/2000 may have limits on the size of stored procedures they can call. The limits typically range from 2000 to 3000 lines of code. See Also: Your PL/SQL or Developer/2000 documentation for details Trigger Cascade Limit Maximum value Operating system-dependent, typically 32 Users and Roles Maximum 2,147,483,638 Tables Maximum per clustered table 32 tables Maximum per database Unlimited
HTHCode:Item Type of Limit Limit Value Instances per database Maximum number of OPS Operating system-dependent instances per database Locks Row-level Unlimited Distributed Lock Manager Operating system dependent SGA size Maximum value Operating system-dependent; typically 2 to 4 GB for 32-bit operating systems, and > 4 GB for 64-bit operating systems Advanced Queuing Maximum per instance 10 Processes Job Queue Processes Maximum per instance 1000 I/O Slave Processes Maximum per background 15 process (DBWR, LGWR, etc.) Maximum per Backup session 15 Sessions Maximum per instance 32K; limited by thePROCESSESandSESSIONS initialization parameters LCK Processes Maximum per instance 10 Shared Servers Maximum per instance Unlimited within constraints set by the PROCESSES and SESSIONS initialization parameters, for instance Dispatchers Maximum per instance Unlimited within constraints set byPROCESSES and SESSIONS initialization parameters, for instance Parallel Maximum per instance Unlimited within constraints set byPROCESSES Execution Slaves and SESSIONS initialization parameters, for instance Backup Sessions Maximum per instance Unlimited within constraints set byPROCESSES and SESSIONS initialization parameters, for instance
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Minimum size of redo is not 64k
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