4 System Limits

The following sections list all TimesTen system limits and defaults.

System limits and defaults
Limits on number of open files
Path names

System limits and defaults

Specific operating system limits may take precedence over these values. For more information, see "Installation prerequisites" in Oracle TimesTen In-Memory Database Installation Guide.

Description	32-bit Value	64-bit Value
Maximum number of replication subscriber data stores. (For Active/Standby schemes, one subscriber value is used by the system.)	128	128
Minimum data store size (bytes). Size includes both the permanent and temporary space required to perform operations on the data store.	32 MB	32 MB
Maximum length for a fixed-length column (bytes).	8,300	8,300
Maximum number of columns in a table.	1,000	1,000
Maximum number of columns in an ORDER BY clause.	1,000	1,000
Maximum number of columns in an GROUP BY clause.	1,000	1,000
Maximum cumulative length of a row's fixed-length columns (bytes).	32,768	32,768
Maximum number of rows in a table.	256 M =31 268,435,256	(2³¹-1) = 2,147,483,647
Maximum length for a varying-length column (bytes).	2²² = 4,194,304	2²² = 4,194,304
Maximum length for a replicated column	4 MB	4 MB
Maximum number of concurrent connections to a data store.	2047	2047
Maximum number of concurrent client connections to a TimesTen instance Note: Some instances may support a slightly smaller maximum number of connections depending on such things as whether the data store is shared or replicated and operating system limits. Most configurations support no less than 2,000 connections.	25,000	25,000
Maximum length of data store names.	32	32
Maximum length of the path name for a data store in an asynchronous writethrough cache group	248	248
Maximum number of projected expressions in a SELECT statement.	32,767	32,767
Maximum length of string specifying a join order.	1,024	1,024
Maximum number of columns in an index (or primary) key.	16	16
Maximum length of basic names.	30	30
Maximum length of displayed predicate string in the `PLAN` table.	1,024	1,024
Maximum length of SQL statement, including the NULL terminator.	409,600	409,600
Maximum number of table references in an SQL query.	24	24
Maximum number of indexes on a table.	32	32
Maximum number of partitions in a table	999	999
Maximum number of concurrent shared memory segment client/server connections per TimesTen instance.	512	512
Maximum size of IPC shared memory segment for client/server connections	1 Gigabyte	1 Gigabyte
Maximum number of allocated statement handles per shared memory segment client/server connection.	512	512
Maximum depth of nesting subqueries.	Equal to the maximum number of table references in an SQL query.	Equal to the maximum number of table references in an SQL query.
Maximum error message length for applications that specify an error message length, for example through a call to SQLError.	512	512

Limits on number of open files

Each process connected to a TimesTen data store keeps at least one operating-system file descriptor open from the time of the first connection until the process terminates. Additional file descriptors may be opened for each data store connection:

Connections to data stores that have logging to disk enabled require an additional two file descriptors for the duration of the connection.
An additional file descriptor is needed for the duration of data store checkpoints issued by the process.
Additional file descriptors may be opened during transaction commit or rollback operations.

For multithreaded applications that maintain many concurrent TimesTen data store connections, the default number of open files permitted to each process by the operating system may be too low.

On HP-UX, the default is 4096 open files per process and may be raised through the tunable parameter maxfiles or with the ulimit command (limit for csh users). You can also set the per-process limit programmatically with setrlimit.
On Solaris, the default limit is 256 open files and may be raised for a session with the ulimit command (limit for csh users). You can also set the per-process limit programmatically with setrlimit.
On AIX, the limit is 2,048 open files, so you are not likely to run into problems.
On Linux, the default limit is 1,024 open files, so you are not likely to encounter problems.
On Windows, the default limit is at least 2,000 open files, so you are not likely to encounter problems.

Most of the open file descriptors are used for reading and writing data store recovery log files. If a process fails to open a log file, the data store is marked as requiring recovery and all current connections to the data store are terminated.

Path names

TimesTen does not support file path names that contain multibyte characters. Please make sure that the installation path, data store path, transaction log path, and temporary file path do not contain any multibyte characters.