C Compatibility Between TimesTen and Oracle Databases

The following sections list compatibility issues between TimesTen and Oracle Databases. The list is not complete, but it indicates areas that require special attention.

• Summary of Compatibility Issues

• Transaction Semantics

• API Compatibility

• SQL Compatibility

• Mappings Between Oracle Database and TimesTen Data Types

Summary of Compatibility Issues

There are a few compatibility issues between the TimesTen and Oracle databases.

Consider the following differences between TimesTen and Oracle databases:

• TimesTen and Oracle database metadata are stored differently. See API Compatibility.

• TimesTen and Oracle databases have different transaction isolation models. See Transaction Semantics.

• TimesTen and Oracle databases 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.

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

Transaction Semantics

TimesTen and Oracle Database transaction semantics differ in a few ways.

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

• Oracle Database can provide both statement-level and transaction-level consistency by using a multi-version consistency model. TimesTen does not provide statement-level consistency. TimesTen provides transaction-level consistency by using serializable isolation.

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

• Oracle Database supports savepoints while TimesTen does not.

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

See Transaction Management in Oracle TimesTen In-Memory Database Operations Guide.

API Compatibility

There are methods from the JDBC and ODBC APIs that have a compatibility issue with cache.

The following sections list methods from the JDBC and ODBC APIs that have a compatibility issue with cache.

• JDBC API Compatibility

• ODBC API Compatibility

JDBC API Compatibility

There are compatibility issues that apply to the JDBC API.

Compatibility issues that apply to JDBC include the following:

• JDBC database metadata functions return TimesTen metadata. If you want Oracle metadata, connect to the Oracle Database directly.

• The set/get connection and statement attributes are performed on TimesTen.

• All Oracle java.sql.ResultSet metadata (length, type, label) is returned in TimesTen data type lengths. The column labels that are returned are TimesTen column labels.

• Oracle extensions (oracle.sql and oracle.jdbc packages) are not supported.

• Java stored procedures are not supported in TimesTen.

java.sql.Connection

The following Connection methods have no compatibility issues:

close()
commit()
createStatement()
prepareCall()
prepareStatement()
rollback()
setAutoCommit()

The following methods are run locally in TimesTen:

getCatalog()
getMetaData
get/setTransactionIsolation()
isReadOnly()
isClosed()
nativeSQL()
setCatalog()
setReadOnly()

Note:

See Transaction Semantics for restrictions for the get/setTransactionIsolation() methods.

The isClosed() method returns only the TimesTen connection status.

java.sql.Statement

The following Statement methods have no compatibility issues:

addBatch()
clearBatch()
close()
execute()
executeBatch()
executeQuery()
executeUpdate()
getResultSet()
getUpdateCount()
getWarnings()

The following methods run locally in TimesTen:

cancel()
get/setMaxFieldSize()
get/setMaxRows()
get/setQueryTimeout()
getMoreResults()
setEscapeProcessing()
setCursorName()

java.sql.ResultSet

The following ResultSet methods have no compatibility issues:

close()
findColumn(int) and findColumn(string)
getXXX(number) and getXXX(name)
getXXXStream(int) and getXXXStream(string)
getMetaData()

java.sql.PreparedStatement

The following PreparedStatement methods have no compatibility issues:

addBatch()
close()
execute()
executeUpdate()
executeQuery()
getResultSet()
getUpdateCount()
setXXX()
setXXXStream()

The following methods run locally in TimesTen:

cancel()
get/setMaxFieldSize()
get/setMaxRows()
get/setQueryTimeout()
getMoreResults()
setEscapeProccessing()
setCursorName()

java.sql.CallableStatement

The same restrictions as shown for the java.sql.Statement and java.sql.PreparedStatement interfaces apply to CallableStatement.

• In a WRITETHROUGH cache group, if PassThrough=1, indirect DML operations that are hidden in stored procedures or induced by triggers may be passed through without being detected by Cache Connect to Oracle.

• Stored procedures that update, insert, or delete from READONLY cache group tables will be autorefreshed within another transaction in an asynchronous fashion. Thus, the changes do not appear within the same transaction that the stored procedure was processed within and there may be some time lapse before the changes are autorefreshed into the cache table.

java.sql.ResultSetMetaData

The following ResultSetMetaData methods have no compatibility issues:

getColumnCount()
getColumnType()
getColumnLabel()
getColumnName()
getTableName()
isNullable()

The following methods run locally in TimesTen:

getSchemaName()
getCatalogName()
getColumnDisplaySize()
getColumnType()
getColumnTypeName()
getPrecision()
getScale()
isAutoIncrement()
isCaseSensitive()
isCurrency()
isDefinitelyWritable()
isReadOnly()
isSearchable()
isSigned()
isWritable()

Stream Support

There are compatibility issues related to streams.

The compatibility issues related to streams are:

• The JDBC driver fully fetches the data into an in-memory buffer during a call to the executeQuery() or next() methods. The getXXXStream() entry points return a stream that reads data from this buffer.

• Oracle supports up to 2 GB of long or long raw data. When cached, TimesTen converts LONG data into VARCHAR2 data. TimesTen converts LONG RAW data into VARBINARY data. Both VARCHAR2 and VARBINARY data types can store up to a maximum 4,194,304 (2²²) bytes).

• Oracle always streams LONG/LONG RAW data even if the application does not call getXXXStream().

• TimesTen does not support the mark(), markSupported(), and reset() methods.

ODBC API Compatibility

Cache in TimesTen is compatible with a subset of ODBC functions.

Table C-1 describes the compatibility of ODBC functions.

Table C-1 ODBC Function Compatibility With Cache in TimesTen

Function Name	Compatibility
SQLBindParameter	Default TimesTen behavior matches Oracle Database behavior. See Binding Parameters and Running Statements in Oracle TimesTen In-Memory Database C Developer's Guide.
SQLBrowseConnect, SQLColumnPrivileges, SQLExtendedFetch, SQLMoreResults, SQLSetPos, SQLSetScrollOptions, SQLTablePrivileges	Not supported.
SQLCancel	There are some restrictions. In particular, SQLCancel cannot cancel TimesTen administrative operations. See the SQLCancel entry in ODBC 2.5 Function Support in the Oracle TimesTen In-Memory Database C Developer's Guide.
SQLGetCursorName	There are some restrictions. See the SQLGetCursorName entry in ODBC 2.5 Function Support in the Oracle TimesTen In-Memory Database C Developer's Guide.

SQL Compatibility

This section compares TimesTen's SQL implementation with Oracle Database SQL.

The purpose is to provide users with a list of Oracle Database SQL features not supported in TimesTen or supported with different semantics.

• Schema Objects

• Non-Schema Objects

• Differences Between Oracle Database and TimesTen Tables

• Data Type Support

• SQL Operators

• SELECT Statements

• SQL Subqueries

• SQL Functions

• SQL Expressions

• INSERT/DELETE/UPDATE/MERGE Statements

• TimesTen-Only SQL and Built-In Procedures

• PL/SQL Constructs

Schema Objects

TimesTen does not recognize some of the schema objects that are supported in Oracle Database.

TimesTen returns a syntax error when a statement manipulates or uses these objects. TimesTen passes the statement to Oracle Database. The unsupported objects are:

• Clusters
• Objects created by the CREATE DATABASE statement
• Objects created by the CREATE JAVA statement
• Database links
• Database triggers
• Dimensions
• Extended features
• External procedure libraries
• Index-organized tables
• Mining models
• Partitions
• Object tables, types and views
• Operators

TimesTen supports views and materialized views, but it cannot cache an Oracle Database view. TimesTen can cache an Oracle Database materialized view in a user-managed cache group without the AUTOREFRESH cache group attribute and PROPAGATE cache table attribute. The cache group must be manually loaded and flushed.

Caching Oracle Database Partitioned Tables

TimesTen can cache Oracle Database partitioned tables at the table level, but individual partitions cannot be cached.

The following describes how operations on partitioned tables affect cache groups:

• DDL operations on a table that has partitions do not affect the cache group unless there is data loss. For example, if a partition with data is truncated, an AUTOREFRESH operation does not delete the data from the corresponding cached table.

• WHERE clauses in any cache group operations cannot reference individual partitions or sub-partitions. Any attempt to define a single partition of a table returns an error.

Non-Schema Objects

TimesTen does not recognize some of the schema objects that are supported in Oracle Database.

TimesTen returns a syntax error when a statement manipulates or uses these objects. TimesTen passes the statement to Oracle Database. The unsupported objects are:

• Contexts
• Directories
• Editions
• Restore points
• Roles
• Rollback segments
• Tablespaces

Differences Between Oracle Database and TimesTen Tables

TimesTen supports a subset of the Oracle Database features.

The Oracle Database table features that TimesTen does not support are:

• ON DELETE SET NULL

• Check constraints

• Foreign keys that reference the table on which they are defined

Data Type Support

Certain Oracle Database 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
• BFILE
• Oracle Database-supplied types
• User-defined types

The following TimesTen data types are not supported by Oracle Database:

• 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 Database NCHAR and NVARCHAR2 data types are encoded as either UTF-16 or UTF-8.

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

SQL Operators

TimesTen supports a subset of operators and predicates that are supported by the Oracle Database:

• unary -
• +, -, *, /
• =, <, >, <=, >=, <>, !=
• ||
• IS NULL, IS NOT NULL
• LIKE (Oracle Database 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 run a bitwise AND operation of two bit vector expressions, TimesTen uses the ampersand character (&) between the expressions while Oracle Database uses the BITAND function with the expressions as arguments.

SELECT Statements

TimesTen supports a subset of clauses of a SELECT statement that are supported by the Oracle Database:

• FOR UPDATE

• ORDER BY, including NULLS FIRST and NULLS LAST

• GROUP BY, including ROLLUP, GROUPING_SETS and grouping expression lists

• Table alias

• Column alias

• Subquery factoring clause with constructor

Oracle Database 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.

TimesTen does not support the CONNECT BY clause.

SQL Subqueries

TimesTen supports a subset of subqueries that are supported by the Oracle Database.

• IN (subquery)
• >,<,= ANY (subquery)
• >,=,< SOME (subquery)
• EXISTS (subquery)
• >,=,< (scalar subquery)
• Subqueries in WHERE clause of DELETE/UPDATE
• Subqueries in FROM clause
• Subquery factoring clause (WITH constructor)

Note:

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

SQL Functions

TimesTen supports a subset of functions that are supported by the Oracle Database.

• ABS
• ADD_MONTHS
• ASCIISTR
• AVG
• CAST
• CEIL
• COALESCE
• CONCAT
• COUNT
• CHR
• DECODE
• DENSE_RANK
• EMPTY_BLOB
• EMPTY_CLOB
• EXTRACT
• FIRST_VALUE
• FLOOR
• GREATEST
• GROUP_ID
• GROUPING
• GROUPING_ID
• INSTR
• LAST_VALUE
• LEAST
• LENGTH
• LOWER
• LPAD
• LTRIM
• MAX
• MIN
• MOD
• MONTHS_BETWEEN
• NCHR
• NLS_CHARSET
• NLS_CHARSET_NAME
• NLSSORT
• NULLIF
• NUMTOYMINTERVAL
• NUMTODSINTERVAL
• NVL
• POWER
• RANK
• REPLACE
• ROUND
• ROW_NUMBER
• RPAD
• RTRIM
• SIGN
• SQRT
• SUBSTR
• SUM
• SYS_CONTEXT
• SYSDATE
• TO_BLOB
• TO_CLOB
• TO_CHAR
• TO_DATE
• TO_LOB
• TO_NCLOB
• TO_NUMBER
• TRIM
• TRUNC
• UID
• UNISTR
• UPPER
• USER

These TimesTen functions are not supported by Oracle Database:

• CURRENT_USER
• GETDATE
• ORA_SYSDATE
• SESSION_USER
• SYSTEM_USER
• TIMESTAMPADD
• TIMESTAMPDIFF
• TT_HASH
• TT_SYSDATE

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. Applications should use the UNISTR SQL function instead of literals.

SQL Expressions

TimesTen supports a subset of expressions that are supported by the Oracle Database.

• Column Reference
• Sequence
• NULL
• ()
• Binding parameters
• CASE expression
• ROWID pseudocolumn
• ROWNUM pseudocolumn

TimesTen and Oracle Database treat literals differently. See the description of HexadecimalLiteral in Constants in Oracle TimesTen In-Memory Database SQL Reference.

INSERT/DELETE/UPDATE/MERGE Statements

TimesTen supports certain DML statements that are also supported by the Oracle Database.

• INSERT INTO ... VALUES

• INSERT INTO ... SELECT

• UPDATE WHERE expression (expression may contain a subquery)

• DELETE WHERE expression (expression may contain a subquery)

TimesTen does not support updating of primary key values except when the new value is the same as the old value.

TimesTen-Only SQL and Built-In Procedures

There are TimesTen SQL statements and functions and built-in procedures that are not supported by the Oracle Database.

With PassThrough=3, these statements are passed to Oracle Database for processing 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.

• ROWS m TO n clause.

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

• TimesTen specific syntax for character and unicode strings are not always converted to the Oracle Database syntax when using PassThrough=3.

  Note:

  For more details on TimesTen support for unicode strings, see Character and Unicode Strings in the Oracle TimesTen In-Memory Database Reference.

  • Supplying \046 converts to the & symbol on TimesTen, but is not converted to this symbol when passed through to an Oracle database. The \xyz notation is not supported by the Oracle database. To send a character through to an Oracle database, pass it as an argument within the CHR() function with the decimal value of the character.

  • TimesTen enables depicting a unicode value (a four-digit hexadecimal number) within a character string with the \uxyzw syntax (for NCHAR and NVARCHAR2 only) where you substitute the unicode value for xyzw, as in\ufe4a.

    The \uxyzw notation is not supported by the Oracle database. Thus, any unicode strings in NCHAR or NVARCHAR2 columns passed through to an Oracle database must be passed as an argument within the UNISTR() function without the u character.

    The following example inserts the unicode values '0063' and '0064', which are the a and b characters respectively. Since we are using PassThrough=3, this statement is performed on the Oracle database; thus, we do not provide the u character as we would if this was performed on TimesTen.

    Command> INSERT INTO my_tab VALUES (UNISTR(n'\0063\0064'));
    1 row inserted.

PL/SQL Constructs

TimesTen supports a subset of stored procedure constructs, functions, data types, packages and package bodies that are supported by Oracle Database.

See Overview of PL/SQL Features in the Oracle TimesTen In-Memory Database PL/SQL Developer's Guide.

Mappings Between Oracle Database 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 Database tables and choose an equivalent or compatible data type for the columns in the cache tables.

Note:

TimeTen cache, including passthrough, does not support the Oracle Database ROWID data type. However, you can cast a ROWID data type to a CHAR(18) when provided on the SELECT list in a SQL query.

The following example demonstrates the error that is returned when you do not cast the ROWID data type. Then, the example shows the correct casting of a ROWID data type to CHAR(18):

Command> SET PASSTHROUGH 3;
Passthrough command has set autocommit off.
Command> SELECT ROWID FROM dual;
 5115: Unsupported type mapping for column ROWID
The command failed.
Command> SELECT CAST (ROWID AS CHAR(18)) FROM DUAL;
< AAAAB0AABAAAAEoAAA >
1 row found.

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 C-2.

Table C-2 Data Type Mappings Allowed for Key Columns

Oracle Database 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(n)	CHAR(n)
VARCHAR2(n)	VARCHAR2(n)
RAW(n)	VARBINARY(n)
DATE	DATE
TIMESTAMP(n)	TIMESTAMP(n)
NCHAR(n)	NCHAR(n)
NVARCHAR2(n)	NVARCHAR2(n)

Table C-3 shows the data type mappings allowed for non-key columns in a cache table.

Table C-3 Data Type Mappings Allowed for Non-Key Columns

Oracle Database 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(n)	CHAR(n)
VARCHAR2(n)	VARCHAR2(n)
RAW(n)	VARBINARY(n)
LONG	VARCHAR2(n) Where n can be any valid value within the range defined for the VARCHAR2 data type.
LONG RAW	VARBINARY(n) Where n can be any valid value within the range defined for the VARBINARY data type.
DATE	DATE TIMESTAMP(0)
TIMESTAMP(n)	TIMESTAMP(n)
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(n)	NCHAR(n)
NVARCHAR2(n)	NVARCHAR2(n)
CLOB	VARCHAR2(n) Where 1 <= n <= 4 MB.
BLOB	VARBINARY(n) Where 1 <= n <= 4 MB.
NCLOB	NVARCHAR2(n) Where 1 <= n <= 2 MB.