Chapter 4: EJB CMP Tuning

Configuring OCC options

To enable OCC, first verify that PCC is disabled, then configure the timestamp mechanism of your choice.

To check that PCC is disabled, verify that the Select With Lock option on the Persistence/General subtab in the EAServer Manager Component Properties dialog box is disabled. On the Advanced tab, verify that com.sybase.jaguar.component.selectForUpdate is not set or set to false. When using jagtool or XML configuration files, verify the properties com.sybase.jaguar.component.selectWithLock and com.sybase.jaguar.component.selectForUpdate are both false.

Specify the timestamp mechanism in the Timestamp field on the Persistence/General subtab in the EAServer Manager Component Properties dialog box. Table 4-1 describes the allowable values. When using jagtool or XML configuration files, set the com.sybase.jaguar.component.timestamp property. If multiple tables are used and you specify a timestamp column, all tables must contain a column with the same name and datatype.

**Table 4-1: Timestamp field values**
To configure	Set the timestamp value to
A timestamp column	The name of a single column in each table that serves as the timestamp to detect update collisions. If the component uses multiple tables, each must contain a timestamp column with this name. The column type can be: A 4-byte integer – this is the default timestamp column type. All processes that update the table(s) must increment the timestamp with each update, or your DBA can create an update trigger to increment the timestamp automatically. The database timestamp type – you can use the timestamp datatype if using Sybase Adaptive Server Enterprise or Adaptive Server Anywhere version 7.0 or later. You must also define a field mapping property to specify the timestamp datatype as described in “Setting field-mapping properties” in the EAServer Programmer’s Guide. For example, if the column name is ts, specify the mapping as: ts[dbts not null] dbts is a logical type name mapped to the timestamp type in the Sybase_ASE and Sybase_ASA database types. If the database does not support timestamps, a 4-byte integer counter is used instead.
A table level timestamp	A table and column name, in the form `ts_table.ts_column`, where ts_table specifies the timestamp table and ts_column specifies the name of the timestamp column in the timestamp table. The specified timestamp table must be separate from the main table. The timestamp tables can contain multiple columns, to allow use of one timestamp table by multiple entity beans. Timestamp tables are automatically created if they do not exist. A timestamp table can be shared among multiple components even when only one column is present in the timestamp table. In other words, a single timestamp value can be shared by multiple tables. This helps further improve performance for a group of read-mostly tables. However, any insert, delete, or update on any of the tables results in all cache entries being discarded. When using a timestamp table, database triggers are required to increment the timestamp for each update, delete, or insert to tables that are mapped to the component or components that require the timestamp. You can set the component property com.sybase.jaguar.component.ts.triggers property so EAServer creates triggers, create triggers yourself, or add code to existing triggers.
All values comparison	Leave blank.
PCC	Set the value to “none” to disable optimistic concurrency control. In this case, you are strongly advised to configure locking as described in “Enabling PCC”.

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