11 Compatibility Between TimesTen and Oracle

This chapter lists compatibility issues between TimesTen and Oracle. The list is not complete, but it indicates areas that require special attention. It includes the following topics:

Summary of compatibility issues

Consider the following differences between TimesTen and Oracle:

  • TimesTen and Oracle database metadata are stored differently. See "API compatibility" for more information.

  • TimesTen and Oracle have different transaction isolation models. See "Transaction semantics" for more information.

  • TimesTen and Oracle have different connection and statement properties. For example, TimesTen does not support catalog names, scrollable cursors or updateable cursors.

  • Sequences are not cached and synchronized between the TimesTen database and the corresponding Oracle database. See "SQL expressions" for more information.

  • Side effects of Oracle triggers and stored procedures are not reflected in the TimesTen database until after an automatic or manual refresh operation.

Transaction semantics

TimesTen and Oracle transaction semantics differ as follows:

  • Oracle serializable transactions can fail at commit time because the transaction cannot be serialized. TimesTen uses locking to enforce serializability.

  • Oracle users can lock tables explicitly through SQL. This locking feature is not supported in TimesTen.

  • Oracle supports savepoints while TimesTen does not.

  • In Oracle, a transaction can be set to be read-only or read/write. This is not supported in TimesTen.

For more information about TimesTen isolation levels and transaction semantics, see "Transaction Management and Recovery" in Oracle TimesTen In-Memory Database Operations Guide.

API compatibility

For a complete list of the JDBC API classes and interfaces that TimesTen supports with notes on which methods have a compatibility issue, see "Key JDBC classes and interfaces" in Oracle TimesTen In-Memory Database Java Developer's Guide.

For a complete list of the ODBC API functions that TimesTen supports with notes on which functions have a compatibility issue, see "TimesTen ODBC Functions and Options" in Oracle TimesTen In-Memory Database C Developer's Guide.

For a complete list of the OCI functions for Oracle database, release 11.1.0.7, that TimesTen supports with notes on which functions have a compatibility issue, see "TimesTen Support for Oracle Call Interface" in Oracle TimesTen In-Memory Database C Developer's Guide.

SQL compatibility

This section compares TimesTen's SQL implementation with Oracle's SQL. The purpose is to provide users with a list of Oracle SQL features not supported in TimesTen or supported with different semantics.

Schema objects

TimesTen does not recognize some of the schema objects that are supported in Oracle. TimesTen returns a syntax error when a statement manipulates or uses these objects and passes the statement to Oracle. The unsupported objects are:


Access Control objects:
Roles
Profiles
Contexts

Storage Management features:
Clusters
Tablespaces
Rollback segments
CREATE DATABASE and DROP DATABASE statements
Database links
Directories
Partitions
Extended Features
External procedure libraries
Object tables
Object types
Object views

TimesTen supports views and materialized views, but it cannot cache an Oracle view.

Differences between Oracle and TimesTen tables

The Oracle table features that TimesTen does not support are:

  • ON DELETE SET NULL

  • Check constraints

Data type support

The following Oracle data types are not supported by TimesTen:


TIMESTAMP WITH TIME ZONE
TIMESTAMP WITH LOCAL TIME ZONE
INTERVAL YEAR TO MONTH
INTERVAL DAY TO SECOND
UROWID
CLOB
NCLOB
BLOB
BFILE
REF
"Any" types
XML types
Spatial types
Media types

Note:

TimesTen can cache CLOB, NCLOB and BLOB data. See "Caching Oracle LOB data".

Passthrough queries that reference Oracle CLOB, NCLOB and BLOB fields are supported.

The following TimesTen data types are not supported by Oracle:


TT_CHAR
TT_VARCHAR
TT_NCHAR
TT_NVARCHAR
TT_BINARY
TT_VARBINARY
TINYINT and TT_TINYINT
TT_SMALLINT
TT_INTEGER
TT_BIGINT
TT_DECIMAL
TT_DATE
TIME and TT_TIME
TT_TIMESTAMP

Note:

TimesTen NCHAR and NVARCHAR2 data types are encoded as UTF-16. Oracle NCHAR and NVARCHAR2 data types are encoded as either UTF-16 or UTF-8.

To cache an Oracle NCHAR or NVARCHAR2 column, the Oracle NLS_NCHAR_CHARACTERSET encoding must be AL16UTF16, not AL32UTF8.

SQL operators

TimesTen supports these operators and predicates that are supported by Oracle:


unary -
+, -, *, /
=, <, >, <=, >=, <>=
||
IS NULL, IS NOT NULL
LIKE (Oracle LIKE operator ignores trailing spaces, but TimesTen does not)
BETWEEN
IN
NOT IN (list)
AND
OR
+ (outer join)
ANY, SOME
ALL (list)
EXISTS
UNION
MINUS
INTERSECT

To perform a bitwise AND operation of two bit vector expressions, TimesTen uses the ampersand character (&) between the expressions while Oracle uses the BITAND function with the expressions as arguments.

SQL functions

TimesTen supports these functions that are supported by Oracle:


ABS
ADD_MONTHS
AVG
CEIL
COALESCE
CONCAT
COUNT
DECODE
EXTRACT
FLOOR
GREATEST
INSTR
LEAST
LENGTH
LPAD
LTRIM
MAX
MIN
MOD
NUMTOYMINTERVAL
NUMTODSINTERVAL
NVL
POWER
ROUND
RPAD
RTRIM
SIGN
SQRT
SUBSTR
SUM
SYS_CONTEXT
SYSDATE
TO_DATE
TO_CHAR
TO_NUMBER
TRIM
TRUNC

TimesTen and the Oracle Database interpret the literal N'\UNNNN' differently. In TimesTen, N'\unnnn' (where nnnn is a number) is interpreted as the national character set character with the code nnnn. In the Oracle Database, N'\unnnn' is interpreted as 6 literal characters. The \u is not treated as an escape. This difference causes unexpected behavior. For example, loading a cache group with a WHERE clause that contains a literal can fail. This can also affects dynamic loading and cache grid operation. Applications should use the UNISTR SQL function instead of literals.

SQL expressions

TimesTen supports these expressions that are supported by Oracle:


Column Reference
Sequence
NULL
()
Binding parameters
CASE expression
CAST

These TimesTen expressions are not supported by Oracle:


CURRENT_USER
GETDATE
ORA_SYSDATE
SESSION_USER
SYSTEM_USER
TT_HASH
TT_SYSDATE

SQL subqueries

TimesTen supports these subqueries that are supported by Oracle:


IN (subquery)
>,<,= ANY (subquery)
>,=,< SOME (subquery)
EXISTS (subquery)
>,=,< (scalar subquery)
In WHERE clause of DELETE/UPDATE
In FROM clause

Note:

A nonverifiable scalar subquery is a scalar subquery whose 'single-row-result-set' property cannot be determined until execution time. TimesTen allows at most one nonverifiable scalar subquery in the entire query and the subquery cannot be specified in an OR expression.

SQL queries

TimesTen supports these queries that are supported by Oracle:

  • FOR UPDATE

  • ORDER BY

  • GROUP BY

  • Table alias

  • Column alias

Oracle supports flashback queries, which are queries against a database that is in some previous state (for example, a query on a table as of yesterday). TimesTen does not support flashback queries.

INSERT/DELETE/UPDATE statements

TimesTen supports these DML statements that are supported by Oracle:

  • INSERT INTO ... VALUES

  • INSERT INTO ... SELECT

  • UPDATE WHERE expression (expression may contain a subquery)

  • DELETE WHERE expression (expression may contain a subquery)

  • MERGE

TimesTen-only SQL and built-in procedures

This section lists TimesTen SQL statements and built-in procedures that are not supported by Oracle. With PassThrough=3, these statements are passed to Oracle for execution and an error is generated.

  • All TimesTen cache group DDL and DML statements, including CREATE CACHE GROUP, DROP CACHE GROUP, ALTER CACHE GROUP, LOAD CACHE GROUP, UNLOAD CACHE GROUP, REFRESH CACHE GROUP and FLUSH CACHE GROUP.

  • All TimesTen replication management DDL statements, including CREATE REPLICATION, DROP REPLICATION, ALTER REPLICATION, CREATE ACTIVE STANDBY PAIR, ALTER ACTIVE STANDBY PAIR and DROP ACTIVE STANDBY PAIR.

  • FIRST n clause

  • All TimesTen built-in procedures. See "Built-In Procedures" in Oracle TimesTen In-Memory Database Reference.

PL/SQL constructs

TimesTen supports a subset of stored procedure constructs, functions, data types, packages and package bodies that are supported by Oracle. See Oracle TimesTen In-Memory Database PL/SQL Developer's Guide for details.

Mappings between Oracle and TimesTen data types

When you choose data types for columns in the TimesTen cache tables, consider the data types of the columns in the Oracle tables and choose an equivalent or compatible data type for the columns in the cache tables.

Primary and foreign key columns are distinguished from non-key columns. The data type mappings allowed for key columns in a cache table are shown in Table 11-1.

Table 11-1 Data type mappings allowed for key columns

Oracle data type TimesTen data type

NUMBER(p,s)

NUMBER(p,s)

Note: DECIMAL(p,s) or NUMERIC(p,s) can also be used. They are aliases for NUMBER(p,s).

NUMBER(p,0)

INTEGER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER(p,0)

NUMBER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER

CHAR(m)

CHAR(m)

VARCHAR2(m)

VARCHAR2(m)

RAW(m)

VARBINARY(m)

DATE

DATE

TIMESTAMP(m)

TIMESTAMP(m)

NCHAR(m)

NCHAR(m)

NVARCHAR2(m)

NVARCHAR2(m)

Table 11-2 shows the data type mappings allowed for non-key columns in a cache table.

Table 11-2 Data type mappings allowed for non-key columns

Oracle data type TimesTen data type

NUMBER(p,s)

NUMBER(p,s)

REAL

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

NUMBER(p,0)

INTEGER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER(p,0)

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

NUMBER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER

REAL

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

CHAR(m)

CHAR(m)

VARCHAR2(m)

VARCHAR2(m)

RAW(m)

VARBINARY(m)

LONG

VARCHAR2(m)

Note: m can be any valid value within the range defined for the VARCHAR2 data type.

LONG RAW

VARBINARY(m)

Note: m can be any valid value within the range defined for the VARBINARY data type.

DATE

DATE

TIMESTAMP(0)

TIMESTAMP(m)

TIMESTAMP(m)

FLOAT(n)

Note: Includes DOUBLE and FLOAT, which are equivalent to FLOAT(126). Also includes REAL, which is equivalent to FLOAT(63).

FLOAT(n)

BINARY_DOUBLE

Note: FLOAT(126) can be declared as DOUBLE. FLOAT(63) can be declared as REAL.

BINARY_FLOAT

BINARY_FLOAT

BINARY_DOUBLE

BINARY_DOUBLE

NCHAR(m)

NCHAR(m)

NVARCHAR2(m)

NVARCHAR2(m)

CLOB

VARCHAR2(m)

Note: 1<=m<=4 megabytes

BLOB

VARBINARY(m)

Note: 1<=m<=4 megabytes

NCLOB

NVARCHAR2(m)

Note: 1<=m<=2,097,152 characters