DB2 Server for VSE: System Administration

Virtual Storage Requirements of Components

The virtual storage requirements for the database manager include the space for the database manager itself, any application programs, buffers, VSAM control blocks, the package buffers, and dynamic storage requirements.

Table 35 and Table 36 provide data for calculating the virtual storage needed for a particular installation of the database manager. The storage required varies depending on the mode of operation (single user mode or multiple-user mode) and the initialization parameter values used when the database manager is started.

The minimum dynamic storage required is NCUSERS x 120000. If the DRDA code is installed, the minimum is NCUSERS x 170000.

Table 35. Initial Storage Requirements of DB2 Server for VSE Database Partitions

	Recommended Minimums for
Formula/Constraints	Single-User Mode	Multiple-User Mode
DB2 Server for VSE Code 1, 12 Message Repository 12 DB2 Server for VSE Control Blocks * Base * Lock Request Blocks NLRBS x 24 2, 3, 5 * Concurrent Scans Storage NCSCANS x 50 2, 3 x (NCUSERS+3) 2, 6 * Miscellaneous LRBs 8 x (First Prime Number > (NLRBS/4)) * Static Agent Storage below 16M NCUSERS x 57500 12 * Static Agent Storage anywhere NCUSERS x 50000 * Working Storage Area 12 * Working Storage Queue Headers 2, 3 32 + (2 + 2 x (NCUSERS + 3) + NPACKAGE x (NCUSERS + 1)) x 68 * Package Control Blocks NCUSERS x NPACKAGE x 72 bytes 2, 3 * Communications Control Blocks RMTUSERS x 552 2 * If TCP/IP Communications is used, add: (NCUSERS+3) x 264+2000 16 * Stored Procedure Caches (76 * the number of stored procedure servers) +(32 * the number of stored procedure server groups) +(for each procedure, 116 +the length of the LE options string (max 254) + (68 * the number of parameters) ) DB2 Server for VSE Buffers * 4 x Maximum of ((the first power of 2 that is >= (NPAGBUF/8)) or 256) + (NPAGBUF x 4144)2 * 4 x Maximum of (the first power of 2 that is >= (NDIRBUF/8)) or 256) + (NDIRBUF x 560)2 Database Control Blocks * Base control blocks * MAXDBSPC x 8 11 * MAXPOOLS x 18 11 * MAXEXTNT x 8 11 Database I/O Control Blocks * NCUSERS x 216 x # of dbextents * Minimum of (64 or NPAGBUF/10) x (NCUSERS+3) x 64 15 VSAM Control Blocks * (NCUSERS x 1024 + 8192) x # of dbextents 4, 16 * VSAM Catalogs 13	3292000 250000 140000 12288 4500 1048 57500 50000 109000 848 72 0 0 0 59040 8864 88000 8000 576 384 2808 1344 119808 81920 --------------- 4288000 7, 8	3042000 250000 140000 60480 12000 5048 287500 250000 109000 5336 3600 0 0 0 125344 17824 88000 8000 576 384 14040 1536 173056 81920 --------------- 4675644 7, 8

Note:

The above numbers are in bytes. 1 If the DRDA code is installed on the application server, an additional 1.8 megabytes is required (this applies to both multiple-user mode and single-user mode). 2 The numbers for multiple-user mode assume the following defaults: NCUSERS (5), NPACKAGE (10), NCSCANS (30), NLRBS (2520), NLRBU (1000), NPAGBUF(30), NDIRBUF(30), RMTUSERS(0). 3 The numbers for single-user mode assume the following defaults: NCUSERS (1), NPACKAGE (1), NCSCANS (30), NLRBS (512), NLRBU (1000), NPAGBUF(14), and NDIRBUF(14). 4 The number of datasets = 13 (10 active dbextents + 1 directory dataset + 2 logs for dual logging) 5 The calculation for NLRBS is: NCUSERS x 2 + (NCUSERS x NLRBU)/2 + 10. 6 In single-user mode, NCSCANS x 50 x 3. 7 If you have coded an accounting exit, add its size to the total virtual storage requirements for both single and multiple-user mode. If you have coded any field procedures, add their total size to the requirements for both single and multiple-user mode. In addition, add NCUSERS times the maximum working storage used by any of your field procedures. For more information, see Field Procedures. 8 Add the dynamic storage requirement of active agents. 9 The calculation for the default NPAGBUF is: 10 + 4 x NCUSERS 10 The calculation for the default NDIRBUF is: 10 + 4 x NCUSERS 11 The recommended minimum assumes the defaults for MAXDBSPC (1000), MAXPOOLS (32), and MAXEXTNT (64). 12 The following always reside below 16 megabytes: 1.3 megabytes of the DB2 Server for VSE Code, the Message Repository, and the Static Agent Storage below 16 megabytes, the Working Storage Area, and VSAM catalogs. If your application is running in single-user mode (SUM), you may go above the 16 megabyte line. 13 Assume 40 kilobytes for each VSAM catalog. The recommended minimum assumes two catalogs: the VSAM master catalog and one user catalog. 15 In single-user mode, minimum of (256 or NPAGBUF/2) x 192. 16 Approximately one-eighth of this will reside below 16 megabytes.

Table 36. Virtual Storage Requirements of DB2 Server for VSE Components in the CICS Partition

ONLINE RESOURCE ADAPTER: Initialization, Termination, 659 000 (See Note 2) and Transaction Display Global Control Blocks 1200 + 8 192 x Number of links from the CICS/VSE partition to the Database partition (See Note 3) Execution Time Code 215 000 Execution Time Control Blocks 3 x Maximum number of CICS/VSE transactions that will access concurrently (See Note 3)

ISQL 580000 + Online resource manager requirements + 45000 for each ISQL user + 200000 for each additional message repository

Notes:

1. All numbers are in bytes.

2. The initialization/termination/transaction display code needs to be in the CICS partition only when the CIRA, CIRB, CIRC, CIRT, or CIRD transactions are active. For certain abnormal conditions, the system internally activates CIRT. (For more information, see the DB2 Server for VSE & VM Diagnosis Guide and Reference manual.) This value is calculated by adding the sizes of the following phases: ARIRCONT, ARI0OLRM, ARIMS001, and ARICMOD. If CICS is not able to load the termination phase, the CICS/VSE system waits until storage becomes available. Shutdown is thus delayed, and the wait can be long. Shutdown must complete its process before online access to the database manager can be restarted. Therefore, it is important that the CICS partition contain enough virtual storage to allow the initialization/termination/transaction display code to run. (To avoid the problem of not being able to load the termination code at a critical time, consider specifying RES=YES in the DFHPPT entry for ARIRCONT.)

3. The global control blocks are maintained until CIRT (termination) completes its processing. If the virtual storage requirement for the control blocks is less than 32768 bytes, CICS provides the storage from its own pool. Otherwise, the partition's GETVIS area is used.

4. For execution time control blocks:
   • This storage requirement does not include the virtual storage used by the application transaction.
   • The maximum number of CICS transactions that concurrently access the database manager is not the value NOLINKS (used by the CIRB transaction). The 3-kilobyte virtual storage area is required for a transaction from the time of the first database manager access until the end of the transaction.
   • During online link initialization, a message buffer of 8192 bytes is obtained. This message buffer (mailbox) is used by the resource adapter to gather all the inputs generated by one SQL statement. The inputs are sent as one contiguous message to the database partition. If the SQL statement generates more input than 8192 bytes, the resource adapter attempts to get a larger message buffer from the partition's GETVIS area.

     If the GETVIS fails due to insufficient storage, SQLCODE -932 and an indication (SQLERRD1) of the amount of storage required are returned to the transaction. If this occurs, either the GETVIS area must be made larger, or the transaction must be run when fewer transactions are active.

5. For online application programs, if the fetch/insert blocking option is in effect, add 8 kilobytes to the CICS partition size for each currently open cursor that qualifies for blocking.

6. The numbers shown in the figure do not include a user-written accounting exit.

7. If DRDA is used, add 1 megabyte to the CICS partition size to allow for the additional code in the online resource adapter.

Figure 124. Recommended Batch (or VSE/ICCF) Virtual Storage Increase

DB2 Server for VSE Component	Recommended Minimum Virtual Storage Increase (in kilobytes)
Batch resource adapter   DBS utility MUM   SUM   Any DB2 for VSE MUM preprocessor (Assembler, COBOL, FORTRAN, C or PL/I) SUM   User program MUM   SUM	250   795 (295 + batch resource adapter storage + message repository) or 4,700 (295 + the database partition storage + message repository   750 (250 + batch resource adapter + message repository) or   4,650 (250 + the database partition storage + message repository   User application size + batch resource adapter size or User application size + the database partition size

Notes:

1. The batch resource adapter uses a minimum of 230 kilobytes of virtual storage in the batch (or VSE/ICCF) application's partition. This value must be added to the virtual storage requirements of the SQL application to arrive at the total VSE or VSE/ICCF partition size.

2. The numbers for the DBS utility and the preprocessors show how much virtual storage must be increased to run these facilities in their own partition (multiple user mode) and in the same partition as the database manager (single user mode).

3. MUM means multiple user mode, and SUM means single user mode. See the glossary for definitions of these terms.

4. For programs running in multiple user mode, if the fetch/insert blocking option is in effect, add 8 kilobytes for each currently open cursor that qualifies for blocking.

5. If you have coded an accounting user exit routine, add its size to the total virtual storage requirements.