Summary information |
|
|---|---|
Default value |
16 |
Valid values |
1 to 2147483647 |
Status |
Static |
Display level |
1 |
Required role |
System Administrator |
Adaptive Server manages transactions as configurable server resources. Each time a new transaction begins, Adaptive Server must obtain a free transaction descriptor from a global pool that is created at boot time. Transaction descriptors are internal memory structures that Adaptive Server uses to represent active transactions.
Adaptive Server requires one free transaction descriptor for:
The outer block of each server transaction. The outer block of a transaction may be created explicitly when a client executes a new begin transaction command. Adaptive Server may also implicitly create an outer transaction block when clients use Transact-SQL to modify data without using begin transaction to define the transaction.
Subsequent, nested transaction blocks, created with
additional begin transaction commands, do not
require additional transaction descriptors.
Each database accessed in a multi-database transaction. Adaptive Server must obtain a new transaction descriptor each time a transaction uses or modifies data in a new database.
txn to pss ratio determines the total number of transaction descriptors available to the server. At start-up, this ratio is multiplied by the number of PSS structures to create the transaction descriptor pool:
# of transaction descriptors = PSS structures * txn to pss ratio
The default value, 16, ensures compatibility with earlier versions of Adaptive Server. Prior to version 12.x, Adaptive Server allocated 16 transaction descriptors for each user connection. In version 12.x and later, the number of simultaneous transactions is limited only by the number of transaction descriptors available in the server.
You can have as many databases in a user transaction
as there are in your Adaptive Server installation. For example,
if your Adaptive Server has 25 databases, you can include 25 databases
in your user transactions.
During a peak period, use sp_monitorconfig to examine the use of transaction descriptors:
sp_monitorconfig "txn to pss ratio"
Usage information at date and time: Apr 22 2002 2:49PM. Name num_free num_active pct_act Max_Used Reused -------------- -------- ---------- --------- -------- ------ txn to pss ratio 784 80 10.20 523 NA
If the #Free value is zero or very low, transactions may be delayed as Adaptive Server waits for transaction descriptors to become free in the server. In this case, you should consider increasing the value of txn to pss ratio.
If the #Max Ever Used value is too low, unused transaction descriptors may be consuming memory that can be used by other server functions. Consider reducing the value of txn to pss ratio.
